Tank swap nuked tank

[Phanntom]

Story so far:

Did a tank swap 2 weeks ago and this is how i did it.
- took 50% of the water and put it in totes
- took the fish, rock and corals and put it in that water
- took the remaining water and sand and put in new tank
- but the rocks, fish and corals and water in new tank
- went from a 50 to 80 gallon tank so I added 30g of new water

Here was my mistake, i never washed the sand enough so I had a huge ammonia spike which killed all my inverts, coral and a few fish.

- I took the remaining fish and put them in my quarantine tank.
- I put the rock into totes (was washed, scrubbed and rinsed) and am leaving it there untill the ammonia goes down, doing water changes every 2 days.

I set my tank up as new, used new sand and water and 1 ten lb piece of new live rock.

Here is my question: How long should I leave the old rock in the totes before I return it into the tank and should I add it all at once or slowly? I like the rock in the totes as it is easier to do a water change in a 15g tote then a 80g tank..

I know i missed some important info so ask away and I will do my best to anwer.
Ammonia level at spike: to high to measure (over 4)
ammonia level of live rock now (before water change) around 0.6 (if i'm reading it correctly)

Thanks in advance for any and all info

Bill..