1 ... darkbasic pro, DB classic is an runtime interpreter, Pro is a compiler (waaay faster), and PRO has things like BSP, terrains, particle effects, shaders, memblocks, slide collision, 3d math commands and multiplayer that are not standard in classic (you can get an enhancement pack that adds memblocks and multiplayer to classic though)
2 ... 3ds will be supported when they put the loaders back after the DB native format is fully implimented, at the moment x is your best bet (I would have thought 3d studio max had x export, should be easy for you to check)
cheers.
Mentor.