I don't believe it is black and white, I admire your ability to write your last paragraph.

I would stay vacationing at Grandma's for awhile, maybe find my own therapist to help me deal with this huge issue. I find it odd that he would have porn where you could find it, knowing you're the porn police? It's like he wants to get caught. I don't think he has or will abuse his daughter, I think he is into porn, not "reality", kind of like you or I might dream of winning the lottery; yes it's possible but the probability is too high for me to even spend any time thinking about and yet I sometimes take paper and pencil and plan what I would do with the money.

I would certainly not leave your daughter in her father's care, alone, until she can understand completely about other people seeing/touching her inappropriately and knows she can and "should" tell you if that ever happens, if you are not there and anyone, especially a man (and include Daddy in there, just because he's a man and she is going to be a woman), asks to see her without clothes or touches her too personally.

It does not sound like your husband is violent at all and if you don't feel he would force your daughter to do something your daughter didn't like, I think you can inoculate your daughter and "train" her it is okay to tell you if she is ever uncomfortable with yours, your husband's or anyone else's touch.