I know AG has a lot on her blog about erotic transference that I've read and has helped me make sense if things. I think having experienced sexual abuse by a male caregiver must make transference and erotic transference so much more complicated also. So it's really no wonder yr mind is going a bit all over the place trying to find meaning with what you're thinking, feeling, and trying to sort out what might be 'real' and what might be plain old projection / transference!
Do you think it's BECAUSE you know nothing will ever happen with your T; that he won't EVER act out in a sexual way with you, that that means you feel safe enough to have the fantasies?
Sorry I don't have any real words of wisdom or great suggestions (other than looking over AGs blog perhaps if you haven't already).
Have you ever talked to yr T about the erotic transference?