2. ERC is excelent bowwood. It's however a bit touchy, so it likes a light backing like rawhide on longer bows, or sinew on shorter bows. You wouldn't want to use the latter on longer bows, as it's weight will slow them down.
Backing and heatbending isn't related in any way. you can choose for one option, both, or neither. If you want to get rid of the twist, heat it out. If you want to back it, back it. if you want both, do both. But be sure to get rid of the twist first
3. vertical bamboo flooring is a excelent core material, but I've heard different stories about it on bows. Seems to be pretty weird stuff, but almost unbreakable. you should definately give it a try.
as for wooden backings on ERC, both boo and hickory might be a little to agressive on the soft and lighter ERC. If you want to back it with wood, Ash or maple would probably be better, but I suggest to keep the back prestine and back it with rawhide. It's more historically correct, and leaves some character in it.
Nick