Pretty much everything sounds good. Buy a tub size that is ideal for the snakes size and a uth that covers 1/4-1/3 of the tub. If the cool side can not stay between 78-82 you can get another uth that covers 1/2 of the tub and another thermostat to keep the cool side at temp. Acurite 00891 is a good temp/humidity gauge, it will give you hot side, cool side, and humidity from one unit. Remember you want to measure the uth temp under the substrate (bedding) so you will want to put the acurite probe under it. What do you plan on using as substrate? Humidity levels you listed are good. As for hides I would get the reptile basics hides, they are very dark, secure, cheap, and come in many sizes so it can have the same hide as it grows.
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