1. It seems to be much easier to get a boa back into a side entrance enclosure as opposed to a top opening like a tank. They don't like to be put down - their instinct is to go up - so they tend to struggle when you try to put them back into a tank from the top. Letting them slip back into their enclosure from the side is MUCH easier!
If you're concerned about your hide, you could go with a slightly higher enclosure - maybe 24 inches high. That should offer plenty of clearance and afford your boa a little extra space. You might go with a shelf option too. Another option would be this model - Boaphile hide box cage (2nd picture down).
2. I have recently discovered radient heat panels and they are wonderful! I would highly recommend an RHP for your boaphile. They are effective and safe. On a proportional thermostat, it won't matter what temp your home is, it'll provide the right amount of heat. I would order the RHP from Boaphile when you order your cage, or, if you've already got your cage, Reptile Basics has them too for a good price and Rich has great customer service and he's always had prompt shipping.