I usually find it difficult to give advice with limited information. Hence, if you don't mind, I would like to ask few follow up questions: What, do you think, would be the best approach to address this issue with him?

He seems to be very dependent on you so you will need to be gentle with your delivery. Whatever your message is (i.e., i cannot resume being available for four hours/day), please make sure to let him know that you do care and love him very much and you are doing this (whatever your decision is) for his well being and for the wellbeing of your relationship.

With that being said, I have some more follow up questions:
- does he have a therapist? if he does not, this should be a good starting point.
- how long has he been in this mental state? has he taken any action to help himself?
- does he have family? friends? a job?
- why are you the only person who is willing to help him?
- how old is he?
- does he realize that he is being selfish? I do emphasize with the situation (after all, I have had my own MI problems for over three decades) but I disagree with the mentality that the world has to bow to my MI; and that people who love me has to be there for me whenever I need them.
- how long has this been dependency going on? and how did it get to this place?
- and my last question, which might help or frustrate you and I sincerely apologize if it does cause some negative feelings: why are you so much in love with him? It concerns me that you did not put the boundaries from the beginning and it got turned into a dependence issue.

Again, sorry for not giving one solid advice but these relationship +MI situations are never black and white and they do require further analysis of numerous elements hence the above questions.