Welcome to BPNet and congrats on the new snake!

You might want to consider hitting WalMart or one of those type of stores and grabbing a small kitty litter pan. Put a hole in it and you have a pretty nifty, very inexpensive and easy to clean bigger snake hide. Most of my adults only have a hide on the warm side as they seem quite comfortable lazing out on the cool side without one (their water bowl is also over there on the cool side). Aspen is a great substrate choice. With heavier adults it's a good habit to finger fluff her aspen especially under the hide once in awhile. Aspen tends to compress under the heavier snakes and doesn't let the heat through as easily (if you are using an under tank heating source).

Do watch that wheeze. It could be some skin over her nostrils from all that stuck shed but it also could be a brewing RI. If you have any concern about her health, a good herp vet is always your best bet. As you know from your previous experience, it's best to get on top of an RI before it gets too advanced. A lot of vets now prefer injections rather than meds by mouth for these snakes with their super duper digestive acids.

As far as rat size, even our biggest female who easily tops 3,200 grams these days never gets more than a small to smallish medium rat offered to her once every 7 days. We feed live rats and find this the best, safest and healthiest option for the big girls. A search through our forums (use Search and put in Live Feeding) will give you literally tons of threads on safe live feeding methods if this snake is used to live feeds.