There's a saying out there....."Once you know something you can't not know it."
In my humble opinion you have done an enormously important thing for you and for Jeff. You have known or sensed that something is amiss with somebody that you love, and it's hard to just stand by and watch someone struggle and/or get in his own way. I hope you can see that even seeking out this site and trying to understand what is going on with him and with you is a tremendous gift. There are hundreds of guys out there (some of them reading this and other posts in this forum) who would feel so fortunate if they had somebody as caring as you try to help and support them.
Your extending your hand (and heart) to Jeff as he struggles with his process is so very powerful. You can't fix it for him, but you can be there for him.....whether or not you end up in a long-term, committed relationship with him.
In the meantime you may wish to see a therapist yourself...as a means of getting clarity about your own issues and learning how to draw whatever boundaries around your own involvement that are necessary to maintain your own individuality and - in the long run - not get sucked into the dysfunctional patterns.
He may not see this right away, but some day Jeff will come to know just how very fortunate he is to have somebody like you who loves him enough to support him as he navigates these rough waters.
I give you an A+ for your good intentions, for seeking information and support, and for being ready to step up to the plate to help a man you love.