1. Sorry to hear you're having issues with the performance of the application, as you said lowering the visuals will make it more usable however Asset Forge is still a fairly performance heavy application. I'll be attempting to further optimize it through updates.
2. I'm not sure what you mean by this exactly, sorry.
3. OBJ is a fairly standard file format for 3D files, you can read our guide on how custom models work here.