The roots were kept wet during the entire repotting session

Unlike last year, I watered the roots several times, as you told me to do.

Anyway, do you think I did a good job on the roots?

I would still do some heavy pruning.

When I repot tropicals (including Ficus), I typically cut all branches with lanky winter growth back to the point on branches where last summer's growth was starting to stretch out as a result of fall's shorter days and lower light intensity.

Surprisingly, If you do cut it back harder now, by summer's end the tree will have grown to a mass larger than it would have grown to had you only left the tree to sort out its difficulties with root congestion (it can't - not even if you could plant it out in the landscape) or potted up instead of doing a full repot.

While I try not to rely on chance, if you don't prune further the tree will probably be ok eventually. The tree I provided images of was pushing lots of new growth within 2 weeks, even in consideration of the fact it was an extremely hard root pruning (almost turned it into an unrooted cutting). The typical response of pushing new growth within 2 weeks will likely be stretched to 4-6 weeks given the rootwork you did and the volume of foliage remaining on the tree; i.e., unless you top prune more.

So it is not enough to have left only two leaves on each thin branch in the upper third of the plant, but should I also cut the thicker branches of the upper third? Did I get it right? Or should I leave the branches and only cut the leaves?

Should I also prune this other ficus hard even though it loses much fewer leaves? --> https://www.houzz.com/discussions/6448887/root-pruning-of-a-severely-root-bound-ficus-benjamin#n=2

Update. This ficus has suffered much more, but it too is showing signs of recovery by putting out new leaves. If you want to compare this photo with the old ones, keep in mind that I moved the branch indicated with the arrow, which is why you find it in a different position (I also blocked it using other branches, but I don't know if this makes sense, given that it is not his natural position). I know that you would have pruned the plant hard so that you could decide which branches to leave, but I preferred that the plant decide because I'm not as good as you.

I'd rather add another question. I noticed that on some leaves of this ficus (you can barely see it from the photos) there is a sticky substance that also tends to fall to the ground. I inspected the leaves and there are no mealybugs so I don't think it's honeydew. What then could this substance be? I remember that 5-6 years ago the plant was in great trouble (I had only recently taken care of it and I was a disaster) and even then there was this substance and I thought it was cochineal because I mistook the wax gland for cochineal (don't laugh at me: D).

IMPORTANT UPDATE. Unfortunately I was wrong: I inspected the plant better and it is cochineal.

It is a plant that is always closed inside but probably weakened when I pruned the roots so drastically a month ago. On that occasion it was outdoors for two hours and I also put it on the ground in the courtyard.

I will use imidacloprid (Confidor by Bayer because here in Europe we don't have the 3 in 1 product you use, here everything is more complicated). Here in Europe the sale of imidacloprid is prohibited (I repeat: here everything is more complicated...) but I have a good supply of it. I will definitely spray it on the leaves for a more immediate action: should I also administer it systemically? I know you think topically is more effective - can I just spray it on? Do I also treat the other ficus and the kentia present in the same room? Even the dracaena and phalenopsis in the next room? I already know that there will be a bad smell and my patients will complain about it: should I leave them out (except obviously the phalenopsis)? Does it matter that the plants would be exposed to the sun for many hours in the afternoon and are not used to it? As you have explained a few times in the past, I will use distilled water (air conditioner water, actually) and add some vinegar to acidify the solution and prevent alkaline hydrolysis. Is alcohol vinegar better than apple cider vinegar? One teaspoon (1-2 ml?) per liter of water? Is this recommended whether idicloprid is sprayed topically or administered systemically?

I noticed that on some leaves of this ficus (you can barely see it from the photos) there is a sticky substance that also tends to fall to the ground. I inspected the leaves and there are no mealybugs so I don't think it's honeydew. What then could this substance be? The first suspect would be honeydew from any of several insects that feed on sap.

I just saw your update confirming scale is the culprit, as suspected.

I will use imidacloprid [and] will definitely spray it on the leaves for a more immediate action: should I also administer it systemically? I know you think topically is more effective - can I just spray it on? There is no need to use it as a soil drench if the product you use is intended for use in spray form (outdoors only). If you want to use an imidacloprid soil drench to resolve a infestation indoors or as a prophylactic treatment against insects with rasping/sucking mouth parts, indoors or outdoors (other than mites), that's fine, though not necessarily inline with IPM principles.

Do I also treat the other ficus and the kentia present in the same room? Even the dracaena and phalenopsis in the next room? I already know that there will be a bad smell and my patients will complain about it: should I leave them out (except obviously the phalenopsis)? To the best of my knowledge, products with imidacloprid are not approved for spraying indoors. Spraying should occur outdoors and the plant remain there until dry. There shouldn't be much in the way of offensive odors if you use an imidacloprid soil drench and make sure you empty any solution from the collection saucer and rinse the saucer. Don't take what I say as the last word. Read labels carefully and follow all directives on packaging.

Does it matter that the plants would be exposed to the sun for many hours in the afternoon and are not used to it? Yes. Spraying in the evening and leaving the plants to dry overnight is a good strategy, or simply use a soil drench for whatever you are treating prophylactically.

As you have explained a few times in the past, I will use distilled water (air conditioner water, actually) and add some vinegar to acidify the solution and prevent alkaline hydrolysis. Is alcohol vinegar better than apple cider vinegar? I can't answer definitively, but I have always used white vinegar (fermented alcohol/ 5% acetic acid). Both types of vinegar contain roughly the same amount of acetic acid. AC vinegar spoils and white vinegar doesn't, though I don't know whether or not the 'mothering' factor affects its effectiveness.

One teaspoon (1-2 ml?) per liter of water? Yes

Is this recommended whether idicloprid is sprayed topically or administered systemically? Yes. Lowering acidity to around a pH of 6.5 or so reduces eliminates alkaline hydrolysis of large molecules with insecticidal properties into smaller molecules with reduced or no insecticidal properties.

Al

I sprayed 5 liters of water and then inevitably the water also wetted the soil. In short (I realized that if you splash a lot of water, you end up administering imidacloprid systemically too). Who knows, maybe I could have used much less water, given that there aren't many leaves and the infestation was just beginning. However, I can tell you for sure that if you water with imidacloprid, the room will smell very bad for at least 7 days, even if you don't leave water in the saucers. So you confirm that watering a plant by putting 1-2 ml of white vinegar per liter of water is not harmful to the plant? I imagine that at 0.1-02% it is non-toxic. You once wrote: "As with many compounds that are potentially phytotoxic, the dose makes the poison".

Imidacloprid applied topically works systemically, and faster because it doesn't have to move upward to the canopy from the roots. It's applied/absorbed where it is needed.

Using vinegar or citric acid to bring pH to levels more favorable for the plant won't hurt, but pouring herbicidal vinegar with 10-20% acetic acid as opposed to the 5% of vinegar, straight from the bottle on a plant is a fairly effective nonselective herbicide, especially for young plants with few leaves; but even then, it's more apt to kill foliage only via dissolution of of foliage cell membranes as opposed to roots as well.

Al