I just want to say that I’ve read your post and this sounds incredibly complicated and difficult.

The way I’m reading the situation is that you’ll need to either:
a. Admit to how you feel about him and have the boundary-setting discussion (even though he finds you attractive nothing will happen between you two)
B. Terminate the therapy - at which point you might be able to explore a relationship if both of you are actually available for that.

I only mention point B because you did have a six year break and only just resumed - it seems like if you quickly terminate now because of the attraction, it would be ethically sort of okay for you to date, because of the very long break.

That said - 30 years is a very large age gap, and you’re smart to be considering whether you ACTUALLY want him, or just the validation etc.