Extreme caution!
You choose to do what you want do.
You are already depressed because of this person.
I stayed in a relationship for over 10 years and my state of mind would bend
in the wind with my boyfriend. You can't help him, he needs a professional, but you can choose what you want which is happiness.
If a man/woman is not stable in their own mind it would not be wise to marry/children at this time. However there is always hope.
My hope for you is that you follow your instincive insight, then your heart.
This man must walk alone through whatever his issues are but not for you.