I am sorry to hear about what is happening with your cat and your partner. Has she previously been normal around him?
I am a veterinarian, and will do my best to help.
You are already doing the first thing I would recommend, by having her spayed. Cats that are not spayed keep going into heat, as I am sure you know, and all those hormones may be responsible. I think there is a good chance this will stop after her spaying.
If not, I would try calming products like Zylkene, Stress Away, or Rescue Remedy.
Having him be the only one to feed her may also help. If you leave out food
all the time, stop doing that and have him feed her small meals through the day.
Probably the spaying will help. Let me know what else I can help with or answer.