I don't know if there's a delicate, non-threatening way to bring it up, but would it be possible to communicate to T that having these restrictions, with no end in sight, are having a negative effect on your relationship with T? That in the long run, it won't be the relationship with J that ruins your relationship with T, but rather the restrictions themselves? Possibly even that the restrictions only make J feel more desirable.
Without knowing him or talking to him, I can't say for sure -- but it seems that T's trying to "protect" the relationship together by making it impossible to have a proper relationship with anyone else. What he doesn't seem to realize is that this behaviour is much more likely to do you in than any external relationship ever will.
Gralson: my husband (works out of town).
Auto: my girlfriend (lives with her husband Zoffee).
The most dangerous phrase in the English language is "we've always done it this way."