In my case, our separation led to our engagement. But he wasn't asking to see other people, the way your guy is. You need to let him go, its clear he doesn't want you enough to forego others. There's nothing wrong with that attitude, or you, btw. Just that you aren't right and/or ready for each other as a longterm relationship.
Don't cling to him. There is nothing more unattractive than desperation.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh