A couple of problems I see, and I'm not pointing them out to belittle you in any way, just trying to look out for your safety. That 212 engine is a lot of engine and your welds look anything but strong enough to handle the torque that engine will put out. Maybe practicing welding a little more would be helpful.
Also a bottom bracket from a bicycle is far from ideal for a jackshaft. You need high speed sealed bearings for a jackshaft. They can be purchased from bearing shops and are worth the cost for personal safety.
Also the secondary drive belt has to run inside the rear triangle, I can't see anyway you could run it outside the rear triangle.
Also did you take rake and trail into consideration when changing your neck angle? Rake and trail can seriously affect a bikes handling.