I hope he has made an appt. to see a doctor about this. He will definitely need some medication to help balance him out. My husband had similar symptoms along with psoriasis. I put him on a gluten free diet for the psoriasis and it helped about 90%.....but I also noticed his paranoia and anxiety(which was worsening) disappeared the longer he stuck with the diet. It sounds far fetched, but maybe try the gluten free diet and see if you notice a change in his behavior. Gluten is found in wheat, barley, rye and possibly oats. When I looked up my husband's gluten free diet-related improvements, there was a lot of information linking gluten to psychological issues. And when my husband secretly cheats on the diet, he literally gets the paranoid look back in his eyes and his anxiety worsens. Food intolerances or food allergies or just plain old bad eating can definitely have an effect on our moods and thinking. I hope this helps. If you'd like to try the diet on him, just leave me a message and I'll help you with it.
I guess continue to do what you've been doing and watch for any signs of deterioration that may be of concern and that need treating.
Encourage him to see a psychiatrist who will hopefully be able to provide an accurate diagnosis and treatment plan.
It sounds like he possibly has severe depression. Some people with severe depression also have psychotic features (depression with psychotic features).
It could be worth considering what happened a month ago to trigger this current state.
I think encourage him to see a psychiatrist and perhaps look to follow that up with psychotherapy.
You could ask him if he would like you to attend his appointment with him as a support person, etc.
I would suggest you arrange an appointment as soon as possible. I think that there are significant warning signs present and I think that these need addressing kind of urgently.