Hand signals are required to be shown from the open driver's side window, not the sun roof :>)

You do have a computer problem, the question is which one? The CEM or the DIM. And I don't believe you can just get a junk yard part and throw it in. There might be programming involved.

You do need a Volvo scan tool to get the proper codes and a good diagnostic.

Computers are expensive. It might just be a re-soldering that is required. Or a larger heat shield. I don't wish to be an advertisement, but Xemodex.com/us comes to mind as really good and reasonable for reconditioned parts. They use your computers, so you will need to take them out and ship them, and then reinstall them, but no programming is involved and the codes are wiped.

BTW, is the rear prop shaft still connected? How do you know that the angle gear is bad? You have a Haldex awd system which might have a need of maintenance (oil/filter change).
--
My back feels better when I sit in a Volvo seat