I can give you my thoughts on these.

1. It depends. I'm all about the soil biology. That biology includes bacteria, fungi, microarthropods, and protozoa. These all work in harmony with each other to make things normal. If you kill off the microarthropods with Grub-X or any other insecticide, it throws off the balance and gives you abnormal soil and possibly poor soil health until those microarthropods can rebuild their population. So for insects, it is best to have a known problem and limit treatment the best you can. If you have to use insecticide or fungicide, it is a good idea to come in 2-3 weeks later to apply some compost to bring back the normal microbes.
2. For a shady spot in your area, look into fescue especially the red fescue. It's too hot now to seed. Sod would work or wait until the summer heat starts to change with cooler evenings. Otherwise there are some ground covers that look like grass but aren't technically in the grass family. Mondo grass comes to mind. It's extremely slow to spread, like fescue, but eventually it will. There are other ground covers that don't look anything like grass that might work in that area.

1) It really depends. I had a Japanese beetle grub problem so bad that several thousand square feet of turf lost all its roots and floated in September. At that point, I had to bring out the big guns, which damaged a lot more of the soil biology than GrubX would have.

So for me, preventative in May makes sense. If a problem with grubs is characteristically minor, I wouldn't recommend it, but might recommend biological controls like Milky Spore or nematodes instead.

At-risk lawns are ones that are well-irrigated, and look rich and green to the beetles (no self-respecting beetle is going to lay eggs on dry, dead soil).

Problems lately have been getting a lot more minor--probably due to the fact that my lawn is a beacon to them, but the grubs can't survive. I also intentionally use Bag A Bug traps to attract neighborhood beetles to a locale where I know they won't reproduce successfully (call it a neighborhood Good Works program). This year so far, I've seen exactly zero beetles, but the season isn't really started yet. Usually I've seen some sporadic ones by now, though.

While I could discontinue the Grub-X, I haven't yet done so and I'm not going to for a while. Problems can get very bad, very fast.

2) Yep, red fescue might be worth a shot. An hour a day is awfully trim, so I might be inclined to mulch that and drop in shade-loving perennials that you don't have to pay attention to. Hosta and bleeding heart can be very pretty.

Sod can be done now, just keep it moist for at least two weeks. Seeding should still wait for August. A simple business-type shade garden should wait until spring.

There are indicators for grubs. If you don't have the indicators then you likely won't/don't have the grubs. The first indicator is a plethora of beetles swarming your porch lights in May. Those are the beetles that lay the eggs in the soil. The second indicator would be the grubs themselves. Right about the 4th of July, dig up a square foot of sod looking for grubs. If you see fewer than a dozen, you don't have a problem. Grass can tolerate a certain amount of damaging activity. If you see hundreds, then you have a problem and should spray. I put out beetle trap in May to see what I would catch. It wasn't much at all. I probably got less than a pound of beetles in 3 nights.

The organic solution to grubs is beneficial nematodes.

Locale does depend for the indicators. 'Round here, the beetles don't surface until July. Grub problems don't emerge until the end of August or early September.

Thanks for all the info, guys. So basically, I should wait a few weeks, and if I have a ton of beetles around my lights I should worrying.

I'll have to give red fescue a shot. It would be an awfully large area to mulch. Is red fescue seed easy to come by? Home Depot?

Damage to your plants can also be an indicator (I don't frequently see a lot around my lights as they're not on for long periods of time, and the landscape lights aren't bright enough to attract significant quantities). My dahlia tend to get shredded, there's some minor damage to the zinnia. They don't touch the marigold.

Red fescue should be relatively easy to lay hands on at some big box stores, and if not you can always get it online pretty cheap. Worst case, just choose a bag of fescue seed that has a majority of red fescue in it--usually called Deep Shade or Shade lawn mix.