Whenever I enter Potema's Catacombs I am floating in mid air in a blue sky. Most of the regular texture is missing. Any suggestions on what I can do to fix this?

Don't take the brown acid?

Make another save while you are in that cell. Shut down and load that save and see what happens. Something similar happened to me in Blackreach.

Means that potema has ascended to heaven for being a good girl

Are you on the PC though? If you are you could try stuff like the noclip function and walking around.