Happy to help.
I would unplug the UTH (heat mat) until you get a thermostat. It's literally the most important piece of equipment we have as snake keepers.
Those heat mats can spike to temps upwards of 120° and cause horrible burns, neurological issues and even death. Your snake will be fine without the UTH til you get a tstat.
Ok, since you don't know what the breeder was feeding I'd stick to small adult mice or even hopper mice for a few meals. It's very important to be consistent though. I'm going to guess the breeder was feeding hoppers. But BPs typically eat hoppers for about 3-5 meals before moving up to small adult mice. So if you get hoppers don't get many.
Hahaha, no worries on getting excited, can't say I blame you. But patience will be your friend when keeping snakes. Just stick to 5-7 days between moving forward.
And I can understand trying a separate feeding tub, but again, you want to be consistent. No harm done though, just a lesson learned
And good job holding off on handling.
No need to be desperate yet, but I understand. Be patient and consistent.
First things first, get yourself thermostat(s). That will keep your snake safe while also making it easy to get your temps dialed in. There are lots of options, varying greatly in price and quality. HerpStat is basically the Cadillac of tstats, but they're a bit pricey. JumpStart is a good option, I've been using a few of them for years with no problems at all.