First thing's first, please don't plug in your UTH! Those get hot enough to burn your snake. Just order the thermostat TODAY and pay for quicker shipping.

Now that the issue of safety with a lack of thermostat has been taken care of, you need to actually purchase the thermostat. The one from amazon works moderately well. It gets the job done, but it's not the best. I have a Herpstat 2 (you would need only an Herpstat 1 or an Intro) and I LOVE it. I cannot say anything bad about it. Temps stay exact, there's an alarm if it gets too high/too low, and it's an overall amazing product. Your snake will be fine with no heat until you can get your thermostat unless you keep your rooms less than 75*. Then I would suggest you buy a lamp dimmer and a heat lamp as a backup until your thermostat cam came on. The other option is to use a lamp dimmer to control the UTH until your thermostat comes in. This is very, very important.

As for the humid hide, you can offer one if you want. Use it as an additional hide (not your cold and hot hides). Make sure the hides are all identical so your snake will choose thermoregulating over the favorite hide. I usually don't worry about humidity too much until they are in shed. Then humidity needs to be 60%+. There are multiple threads on here about how to achieve that with a tank. Just be warned: it will be a pain to keep those temps.

If you really want to do what's best for your baby, you might consider a cage like a T8 from Animal Plastics. Those kinds of tanks (any brand of those tanks, really) keep humidity and heat pretty well and it won't be such a nightmare for you.

As for feeding, you can offer a live mouse any time. I'd try to feed live for a couple of feedings before you switch over to frozen.