I just compiled a fresh build and rechecked this bug. It seems to me all the mentioned bugs are fixed.
1) The view correctly updates the angle values after applying the boolean operation. I am not able to get an inconsistent view anymore.
2) I'm not able to crash FreeCAD in any way I tried.
3) After applying the boolean OP, nothing besides the boolean object is shown. But I'm not able to show the inner boolean body alone anymore. So as far as I can tell, after applying the boolean, the inner body is non-modifyable and not showable on its ownanymore. (Which is a bit consistent on how Bodies work, but still a bit sad.)
Only thing that is a bit irritating:
1) create again two bodies with a cube each. Set the rotations to 5° and 10°. Result: They're 5° rotated relative to each other.
2) Now apply a boolean. The cubes are now 10° apart, rotated by 5°. This makes sense from how the bodies are represented. But maybe the transformation of the outer body should be applied to the inner body during booleanization. That way the bodies would stay in the same position.
I can't find my login on the bugtracker right now, so I can't comment there. IMO this bug can be closed. Nice job!