Me [30F] with my boyfriend [33M] 8 months, requesting distance

I've been dating Adam about 8 months. He was upfront in the beginning saying that he was still dealing with the aftermath of a 5-year relationship that left him with insomia.

After 8 months, he is still struggling. He recently asked for distance, but affirmed that I'm amazing, patient and kind. We were seeing each other once a week but now I haven't seen him in a month. He hasn't told me directly what happened in his last relationship, but I suspect his ex-girlfriend had a mental illness and he felt obligated to take care of her support her emotionally frequently.

How can I balance being compassionate with my long term goal of finding a marriage partner? How can I help him if he doesn't open up? For those of you who left a relationship that involved mental illness, what did you need in your next relationships? For reference, I do not have a mental illness.

tl;dr: How do I support someone recovering from a past relationship involving mental illness?