You can use a lamp dimmer, the ones that go for $10-20 at home improvement stores. That's what I use, paired with Ultratherm heat pads which are relatively low-heat anyway.

But lamp dimmers aren't nearly as reliable, since you can't pick the exact temperature. But some control is better than none. I haven't had any problems with my Ultratherms on dimmers. If you've got several snakes and aren't on a budget, and you're using a higher wattage heat source, it's probably a good investment to get a sturdy thermostat. From what I've seen there are decent ones that sell for $30-50, but I can't personally recommend any.

A larger bowl will help with the humidity. Drowning won't be an issue - BPs don't usually seem to soak or drink much, anyway. You can also boost the humidity by adding more insulation to the cage (especially if it's an aquarium).

Hope that helps at least a little. I'm sure someone with more experience will pitch in. Good luck.