The room doesn't need to be dark at all for film developing as long as you use daylight tanks and load them in a dark bag. You only need darkness for printing.

I agree that your intended darkroom sounds very small and would suggest that you use the laundry or bathroom instead. Black window-drapes taped on will block the light well, plus a towel under the door gets it quite dark enough to print, especially at night.

As to sensitization, fixer isn't generally much of an issue and it definitely doesn't cause mood issues. It can smell bad and if there's a rotten egg smell (H2S) due to the fixer being really old then that is a bit toxic but ventilation (or fresher fixer) will deal with that issue.

You can become contact-sensitized to some developers (metol), and especially colour developers. Gloves while printing fixes that problem for B&W, and don't do colour prints in trays.