I cycled with live rock and dosed ammonia in my 29g tank. It took me about a week to cycle that way. I also had good quality rock and sand that was taken from someone's tank. You definitely shouldnt cycle with ammonia dosing with fish in the tank. Have you called the lfs
and see if they can hold your fish for a few days or weeks? Some stores will do that to keep your business.
You are in a tough spot, I know but the chances of all those fish including the tang surviving is gonna take some serious work. You can do it though so dont get too discouraged.
I dont think I would add any more LR
right now cause it may produce more ammonia. I think you do need more lR
though for that 85, you should aim for between 1 and 2 lbs per gallon. It looks like a great tank so far. And I love your tang.