1) with your air question I guess the input I could give there would be to buy 8 more 5" disks and run 2 disks per tote. The more air the better and this will cut u down to only 4 ports to block off on the adapter.
2) I have never used FF nutes but as for mixing, you can do that anyway you want to. Using your 10 gal estimate you can fill the tote and add directly to tote and stir or you can put 9 gals in tote and last gal mix 10x strength or lastly mix each gal seperatly. I would go with #1 and just mix all in tote.
3) Make sure you rinse and soak that Tron in PH balanced water until the water you are soaking in stays at the PH you started with while soaking.
4) Yes your gonna need another light. Using the batwing style I hope you have a way to deal with heat.