1. I housed mine since he was a babe. He is getting big and currently he is in a 41 qt which many recommend for full grown adults. Imo, never hurts to go big as long as 1. Keep it 'cluttered' ie lots of hiding places and decor 2. Snake eats consistently and seem do be doing well.
2. Yes. Identical hides.
3. Sorry can't help you with this one. My room temp never goes below 77 in my coldest room. When it gets colder like we have cold fronts in South FL, I turn on the heater because ALL my animals including the furry ones will appreciate that. I would not use lights or CHE for tubs unless you know what you are doing or someone who does gives you the instructions.
4. Can't answer that. I don't like to project human feelings to what my pets really feel. What does it mean to be happy for a snake? To be able to compete for and choose their own mates? Well then he or she is most certainly not happy. The general consensus in the reptile hobby is if it eats for you and breeds for you, it is happy. Most bp's eat better in tubs so I guess it can be happy under that context.
5. Use a thermostat.
By happy I mean not stressed im not projecting my feelings onto him