Set $origin qc, it allows rotating

Import .smd

Don't bother. You can export the model with all bones, studiomdl will strip unneeded bones anyway.

Yes

Wait for update. For now you can revert to older

Bike bones are embedded into armature along with tank skeleton.

Ideally both bike and hulk are one model, with parts are either one mesh or separate bodygroups.

You can try adding blendlayer command for sequence with specified range of blending.

https://github.com/Artfunkel/BlenderSourceTools/releases/tag/2.10.2

Noesis

replace , with . in smd file