If I were you, I would either go with a male Colombian or a male of female dwarf boa. A Nic wouldn't be a bad idea. I have quite a few Nics. The males are about the size of a male ball python and the females are around the size of a female ball. They can get a little longer, but they do not get very thick around.

About the attitude, some have it and some don't. I have a couple that like to strike, but most are very docile.

You can keep the dwarfs in tubs. My males are in 32 quart tubs, and my females in 41 quarts. Another option is a PVC cage. Three or four foot would be good for a female and three for a male.

Colombian males will need a four foot cage.