I am writing this in a tram on my way to the library because I'm not strong enough mentally to be with him for a complete day. Yesterday I read "everything" about this affective disorder + tried the ways of communication that were recommended on self help websites, it worked OK/helped me lots.
Advice boils down to: 1 Stay friendly or at least factual, 2 Be fully honest, 3 Explicitly mark consequences, act them out fully, be consistent.
Most important: Care for yourself!

Obv this is the reason for my leaving today, I'm intending to limit the hours we're together for MY benefit. In parallel I'm willing to observe this/us next week bc on Wednesday he has an appointment with a psych to discuss new medication. I'm calm, conscious, angry, sad and anxious at the same time, tears flow as rivers, I'm adulting so hard like I never did before, with/for myself, with/for him, flipping between "We got this, who else but us?!" and "I have to leave".