I'd get a bigger heater and keep the other one for an emergency.
As for water changes, if you don't have a sump/ato you would remove water from your dt and make sure not to expose the corals. It doesn't matter to much for LR
as long as it isn't out for a long period of time. This shouldn't matter as when you are going to do a water change, the water should be heated up to the temp of your tank and have been mixed. I use a 5 gallon bucket with a spare heater and spare powerhead. Plug both in and leave over night.
If you just put your shrimp in last night, I wouldn't even be testing nitrites or trates. It'll take awhile to build up all of the BB you need. I'd only test ammonia until it is all gone and see what the nitrites are up to as they will be slightly behind. In terms of water changes, I wouldn't change your water until you are done cycling. Once you have 0 ammonia, 0 nitrite, and only nitrates left, dose the tank again to make sure that the ammonia vanishes in a short amount of time, like 10 hours. If this is so, then do a large water change and you are officially cycled.