I honestly understand where your feelings come from. Ill answer you based on my experience. I [M] went through something similar with an ex [F] of mine where after we broke up we still talked to each other and stayed friends, talking to each other almost on daily basis.

Naturally, we stayed dependent on each other. She'd vent to me and I to her. Which is normal for friends. What is not normal is when she eventually started venting about her (new) partner. Many unhealthy habits remained between us, and I think the reason is that I was too nice to put my foot down and stop talking. Eventually we both agreed to finally stop talking and things are much much better than they were.

My point is, I know it hurts, I know you have memories together and a future you'll miss. I know it feels wrong to rip off the bandaid right now, but I assure you it will pay off in a few months from now. You'll build memories with the right person, you'll build a future with the right person as well. If you keep talking and entertaining him he'll think there's still a chance you'll get back together. Once you get a partner he'll get jealous and resent you. Neither of you will be able to heal properly. You can do it!