Just tell him to call you when he's completely done with his current FB. Better yet, just ghost on him.
Seriously... he's outright telling you in his actions that he's not opposed to taking what you're willing to give him so he continues to pursue but don't bother expecting anything other then to be his place-filler until he's back on with her.
Next him... It's what your gut is telling you to do hence why you started this thread.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion