Hi Eleny,
I am sorry you are in this position. It can be very worrisome and very burdensome when someone depends upon us so much.
I think you are going to have to decide to take care of yourself first.
It sounds like you are ready to let go of the relationship?
I think you have to lay some ground rules and be honest about feeling trapped.
I feel it's possible to do this kindly. Speak from your heart.
Please seek therapy for lots of support and so you are less likely to fall into the same/similar trap again. Rescuers can feel great about rescuing, until they get burnt out! This situation had initially served a purpose for you both.
I hope you can terminate this relationship safely for all. In the end, you are not responsible should your friend decide to harm himself over a relationship break-up.
Keep posting, as many here will likely share ideas with you!
Be safe!

WC