You are getting too many opinions. Asking here will just add more confusion until you are completely paralyzed by information overload. At least my opinion comes with written explanation you can check out for yourself. You will also get opinions after this which may contradict mine, so that isn't going to help.

KBG will not do well in shady areas. That is the main reason many people get a fescue/KBG mix of sod or seed. Seed is out of the question for this time of year, so sod is your choice. If you have a lot of shade, then 100% KBG might be a nightmare. For shady areas, fescue will predominate. You can overseed these areas with more fescue in the fall if you want to improve the density and help keep weeds out next season.

I believe compost is overrated. Since it has been the preferred choice for organic gardeners since the 1930s, there is a lot of resistance to my opinion; however, there are a lot of lawn folks who are very happy with the use of alfalfa, soybean meal, and milorganite. The best way to improve your organic matter is to get grass roots into the ground and to feed organics from the top.

You have realized a weakness in a full organic approach. Once weeds are established, it can be overwhelming to get rid of them. Sometimes a one-time spray with herbicide can save you hours of time and weeks of frustration looking at your slow progress in de-weeding. But if you continue on a full organic fertilizer routine, you will quickly overcome any negative effects of the herbicide on the soil microbes. Just because you use a chemical herbicide does not cancel out your organic history of fertilizing. "Going organic" has as many definitions as does "vegetarian." Most of the lawn gurus I know follow a mixed approach of using organic fertilizer all year long until the last application which they use a high nitrogen, fast release chemical fertilizer. Along the way they might spot spray some clumps of weeds which have gotten a start for some reason. Generally that is minimal, though, due to their diligence in the lawn - these folks really are lawn nuts. By spot spraying they are not subjecting the entire lawn to herbicide.

Tupersan is a preemergent herbicide. It will have no effect on your dandelions. Usually dandelions are most affected by a product like Weed-B-Gone spray. Weed-B-Gone is a selective type herbicide which only kills broad leaf plants. It has no effect on grassy weeds. Get it in a container that connects to your hose and spray the plants individually. You only need to moisten the leaves of the plant, not drench the soil. There are some handheld spray hose attachments which allow you to screw another hose thread attachment on after the hand valve. I would use one of those to control the application of the herbicide. Or you could use Weed-B-Gone and pour it into an dial-type hose end sprayer like the Ortho brand available everywhere. If you do not use all the product in the Ortho sprayer, you can pour the remainder back into the original bottle. The Ortho has a flow control trigger built in. As for the heat in MIl, you don't have to worry. There are limits but I think you're fine. If you use the spot spraying approach you should be able to do that with no effect on the turf.

My opinion of corn gluten meal as a preemergent herbicide is that it is worthless. I applied CGM at a rate well above the suggested rate every month for a full season and seem to have as many weeds then as any month or year at this house. However, as a fertilizer, it is the best organic fertilizer you can get. Unfortunately the cost makes it out of most people's range especially considering alfalfa is so much less and seems to work about as well. Proper watering and mowing are much more important to control weeds both pre and post emergence.

I've never heard of waiting a full year to do anything following any type of spraying. If you kill the weeds now, Mother Nature will fill it in for you by next June. For your area with the new soil and no existing grass, you can use RoundUp, a nonselective herbicide, to kill everything. Spray it once, water for a week to induce any new seeds to sprout, and spray again in a week to kill the new sprouts. Wait a day or two and you can put the sod down.

Weed B Gone liquid spray products recommend that you wait anywhere from 1 week (Weed B Gone CCO) to 4 weeks (Weed B Gone Max) after application before seeding.. I don't use granular weed killer as they don't work for crap, so I can't say how long after their use before you can seed. Spot spraying works best when done with a tank sprayer and concentrate.