I'm in the planning stage of a very similar setup. I've done a few grows previously but years ago. I have been readying everything I can find and have built up a pretty solid knowledge base. I'm building my room in a basement so no tent needed although I will use a prefab tent for veg. I am about 3 weeks from building my room. I look forward to following your progress. You seem to have done your homework.

I'm doing a soil grow too and will be using the formula provided by stinkyattic in this noob guide. Soil, nutes and such are discussed at length. You should re-read if you only gave it a skim.

My first reaction is that space will be a premium in the flower tent with this setup. Doable to but a tight fit. Why not just buy prebuilt tents and forget about the panda? BTW panda is better for your situation as it is lightproof. Mylar is not.

You should have no need for the intake fan - negative pressure should do the trick although there may be considerable movement with the panda film. Also, with prebuilt tents you could daisy chain the fan exhaust between the two. Not sure if that was your plan or not but would be much easier with grow tents.

Yes, your flush will be longer - 10 days or more optimal, 7 days at least.

Nute routine - go by the directions but also see the noob guide referenced above. Stinky covers that in detail.

Good luck. You are on the right path. See the sticky in my signature line for some good setup material.