So why does he want to be w/her then? Do you know @toomuchreality ! Is it for the role of "Wife," minus the intimacy. Of any kind? Why can't they then be the friends, and you the lover. . . I guess, I'm just confused, but as always; I'm sure it's a lot more 'nuanced,' than that (it always is). There could maybe even not be so hot or reasonable & explainable / explanation for WHY - it is - he wants Her, to be his 'wife?' Just Because... That's what he's always had in his head, and / or he's not being honest about some of the other things. Or he wants you to be the GF/or the Mistress, perhaps? If she's jealous & reacting in that bad of a fashion: then that suggests all is not kosher as it seems, or may be seems - to him, & in... his head? Very delicate & complicated situation you've found yourself in & what I might do, if I felt it was worth the risk: wouldn't harm the friendship irrevocably & so on. . . is to present him with - not necessarily an "ultimatum," per se~ but more of a ... this is how it is/or this is how it would have to be; in order for us to be in a committed & exclusive relationship that is romantically inclined or oriented. As opposed to the more casual, friends who snuggle, on occasion - or when, "the moment of inspiration," arises. Which, if every-thing he says is true. And there truly are not any others. You would tend to happen more frequently than not. But not necessarily, I suppose (either). In any event, or case, decide or make up in your own mind what you'd like first. Perhaps it is best to just... 'Not rock the boat,' keep things afloat. And then remain perennially unhappy. Or, I dunno! I really, really don't. Only you can decide how much one thing means in comparison, or versus the other. For instance, if you go all-in, and lay it out flat, or state that you really do want to be in a relationship with him. But only on condition that he leaves his current, under the current terms. At least that way, then, you would know, and see, "quite-clearly" or so it would seem (to me)--just where it is you stand. If he picks her, over you, even sans romance, or physical and all other forms of intimacy. Which, maybe he's the sort that doesn't desire & crave those others, at least not to the certain degree that you place emphasis on, or to? That's always a possibility too, or as are, there a million other(s) - I suppose! ;D Good luck, with what ever you decide, and I hope it turns out the way you want it to. : ) Peace & I hope I haven't said any-thing too inflammatory; for if I have, all you have to do, is to: 'consider the source,' & that being of one, or me. A ZERO. or In-Complete, at best~!* HA 
Later.
Later.
