This dream clearly shows the stage where you are in recovering from the breakup of your relationship. (Who initiated it? And who wanted it the most, you or him?)
In real life you imagine he's already "talking to someone else" because that's the typical way that youngish people's relationships start via online contacts--where the normal shyness is avoided because there's no eye contact, so people shift rapidly into stronger rose-colored images and attitudes toward each other, that are based on idealized images that lack reality checks. (I'm dividing your dream into a series of scenes with their own psycho-logic:
1. Taking selfies: Symbolizes focusing only on yourself, together with friends--probably female: So there are no pairbonds with erotic partners in the picture anymore.
2. This opening scene reminds you that your exBF is going away to do his own work. His focus is NOT on you or a pairbond with you. He is NOT disabled in this scene.
3. Your reaction is to identify with your "friends" (are they all women?) in "blowing off the awareness that he's really leaving to do his own work in a world beyond yours. So you're repressing your loss and hiding it from yourself by substituting your friends' companionship for his. [This is a normal & healthy way of coping with loss, but it leaves your grieving for a later time.]
4. So now he shows up in your dream as a character who can't walk and can barely breathe. Not walking symbolizes that your relationship is not going anywhere now--that it would need external help, or YOUR help to progress any further. Also he cannot breathe without added oxygen, so his flame, and thus the flames of your love are in danger of dying out.
5. Your dream ego thinks he's been hiding this development from you. [But the dream has already showed that you have blocked out your own awareness that his life energy was turning elsewhere--which you remember from your waking awareness a few lines later.]
6. Now a voice announces that your internalized (possessed) image of your ex is dying, and the emotional reality hits you with crying.
7. Some masculine part of you says YOU have to act to heal that. Your own thoughts promptly agree with that by inventing another GF that isn't good for him--or more accurately doesn't "feel good for him" to you: because you still have a loving relation pattern in your brain that feels good, and any replacement of that (your loss) would feel "not good." His (typical male) effort to quickly "move on" by assuring himself that he can get another woman as quickly as he wants, feels sickening to you, because he could be dying in your merged couplehood already. [Your own ducking under the covers of girlfriends just having self-focused fun is more innocent--because it's equivalent to regressing into teenage girlgang mentality & solidarity. It's serving the same purpose of repressing the awareness of your&his loss, except that it leaves more room for you to pick up the erotic torch for him again if you want to. Of course HE could do the same for you if he wanted, but YOU could not be sure of that, and NEW LOVE often chases away old love, while girlfriendship does not.] So you could be at a disadvantage in this game of post-breakup "truth-or-dare."
8. So the final scene shows that your exBF is actually keeping you in his music studio, where your playing around creates the mythic atmosphere of being a musical ensemble, of your ego's being unified through the creative play with music. Looks like a "happily ever after" except that it's NOT just you and him as a couple going down the road of life, even though he is walking around. It's him and your group of friends [are the ones in the dream really HIS friends too?]
So to find out what the ending means, we have to explore how it is similar to and DIFFERENT from what you are aware of in real life. Could he be a man whose most enduring love relationship is really with his music? If that's true, then your continuation as his lover after this pause (that may be refreshing him, and MIGHT, you hope, turn out to be disappointing) is over--would be related to how well your needs and relationship behavior fit into the supportive role of "current female lover" and hence finish better than any other woman he might flirt with. [I'm only suggesting this scenario IF he really does love music more than any real woman--which was true for the Beatles until Yoko (a very determined narcissist) stole John's soul away from the group. And other factors could play a role like his and your ages and your levels of maturity, and the duration of your relationship as lovers until now. But it sounds like your commitments to a shared future have been pretty shallow, which would be in normal range if you're under 30.]