12 bolt questions

[rhm63]

I have a 1963 c10 step-side and it appears that I need to rebuild the rear diff.
It needs a new pinion seal for sure, but there is some play, so I think i need new bearings too. I have done a ton of reading about the rebuild so I don't need advice there. However, I do have a few questions.

It is a 12 bolt, but it only has 11. In the picture you can see some old leakage at ~1 o'clock. I am hoping that the other bolt just fell out. Is the housing ruined if the bolt has been broken off in it? Any ides what to expect?

Is it totally unadvised to try to replace the bearings while the axle is still on the truck?

Most of the kits include wheel bearings too, can i just replace the bearings in the diff without pulling the axles?

Thanks