Your temp is way too high for zebra danio's, they're fine in the low 70's. Same with the hillstream loaches; warmer water holds less dissolved O2. Nitrate needs to be kept below 20 ppm for the fish, not an issue for cycling though.
As for numbers, you can actually put quite a few danios in a 55. Forget the 1"/gallon standard, it's really not applicable IME. The real concerns are the fishes behavior (territorial or schooling) and water quality. As long as they aren't fighting over territory and you keep the water clean you can easily double or even triple the 1"/gallon standard. Last month I culled a load of Cryptoheros cutteri cichlids that had grown out from a spawn last year in a 55. Most were 3"+, breeding size adults, but weren't actively breeding because the temp in the tank (basement, no heater in the tank) was below 70. I counted 80 fish, well over 200" total, when I cleared out the tank. They were all fine and healthy, none stunted or beat up. That tank is filtered by 2 aquaclear 70's and an air-driven hydrosponge filter.
My 30 long BN breeding tank is similar, I just moved 50+ ~1.5" juvies into a 33 long for further growout. The 30 houses 4 adult BN, 6 L-333's, one spawn of smaller (~1") BN fry, a couple hundred endler's livebearers, and every month or so I thin out several hundred ramshorn snails. The tank is filtered by an eheim canister and 2 air-driven sponge filters. The canister flow tends to slow down between cleanings, sometimes almost stopping, but the air keeps the water moving. The tank is loaded with Najas and duckweed, the fast-growing plants keep the nitrates low even with the large bioload. That tank has been running that way for several years now, and I regularly move dozens of healthy BN and endler's out of it.
You'll need to add fish in groups, not all at once, to allow the bacteria to adjust to the increased load.
