As far as the power goes there's a certain depth and wire guage you must follow if an inspector is commin through, I believe. With soil the best thing is (for me) that is holds the nutes as well as buffers the ph. Yes I'd add 5ml of cal/mg(becareful 2 types high N for vegg and high P for flowering, use according to cycle) and do this every time. I add 1st, raising my tds to round 150 from nothing(2-12 usually).
What nutes do you use? Here's an example of my weekly feeding. 2 50 gal drums w/ tap (chlorine here)water well airrated(24 hours @ least) I will add Vodoo, Parrahna, Tarantula(good stuff for roots,really really good)and a tad of molassis. If the ph needs to be bumped up a bit I'll add Barricade(this has never needed to be dropped)This is done in only 1 barrel. Then I attach my feeding wand to the pump and water. I'll transfer fresh water to the left over water in the other barrel. The next day I'll add nutes ( up to 1100, but never over.Depends on the stage of life. 600-800 for clones)ph it and feed. Then its water for the next 5. If your gonna do an entire room full you may need 3 50 gal barrels.
A suler burner is basicly a 60 watt heat lamp w/ a cylender(can't spell for crap) tightly around it. You put it up high and w/ the exaust fans off, plug it in and add 1 tsp of sulfer on top. The sulfer turns vapors and coats the leaf. I'm pretty sure it raises the ph so the growth is inhibited.
If your gonna do a room you may want to step away from the R.O. water and utalize the tap. R.O. process is very waistful