1. Generally, PWCs will replenish the depleted elements in your tank, so you really shouldn't have to dose, as you would if your coral "bio-load" is high.
2. Wattage is not as important to most fish and inverts (shrimp, snails and such). So you could go with a basic set up.
3. 1.5-2Lbs per gallon is suggested for proper bio filtration, if you have that, you can go filterless. I use my filter for extra water movement and to run carbon, if needed.
4. I don't have one, but the more water you can get, the better. You can also use the fuge as a pod producer and keep macro algae in there to help filter your water and remove additional nutrience.
5. I believe the flow rate starts around 5x (correct me if I am wrong). I believe flow rate in a FOWLR
is more for the fish's health and water movement, to prevent dead spots and also surface ripple for a stable pH.
6. Not really, IMO
One thing to add, that sandbed might be a little too deep (this of course is an opinion). Mine is anywhere from 2-3 inches in spots. If you get too deep of a sandbed, you could have problems with noxtious gas pockets.
I would wait for some other people's experiences.