OP, I am sorry you are in this position. My DD3 (14) has suffered with mental health issues for various reasons over the last few years. I too have a DH (her dad) who tends to be rather insensitive, although much more just in what he says (motor-mouth who engages mouth before brain) and the way he determinedly misinterprets or misconstrues anything he is told, which I know can be equally as damaging. It is hard, and you are perpetually caught between a rock and a hard place.
You have my sympathy, but I speak from experience when I say that I do think you need to provide your DD with a better safety net. I have learned (again through experience), that not everything about DD needs to be told to DH, and indeed it is often better if it isn't. I no longer involve him unless CAHMS, school etc. require both parents. I go it alone with DD.
I have made it clear to my DH that his blunt ways of speaking make him unsuitable to be regularly involved here even though he means well. I have pointed out before how he has misinterpreted stuff, been totally tactless (tact and diplomacy are not his middle names) and he accepts this. I give him no option but to accept it because much as my DD does love him as her dad, she cannot cope with some of his reactions and wants me rather than him.
So we keep things generally between DD and I and her older sister, to whom she is particularly close. DH occasionally asks in general terms how things are going and gets an equally general answer, which he accepts. I am fortunate in that he accepts that this sort of delicate thing is not his forte.
On the one memorable occasion I did tell DH very firmly to butt out. It was following an appointment at which both parents were requested (so I couldn't stop him being involved there). On the way home afterwards he began motor-mouthing and expounding about how he expected things should be and was upsetting DD. CAHMS too told him at a later appointment that his interpretation had been wide of the mark. He has played no further part.
Your DP should not be photographing your DD without her consent full stop. He should apologise for that and also for labelling her a "bitch". It comes across as creepy and an invasion of her privacy.
What if she told her CAHMS worker that her Dad photographs her in her workout gear? They might then interpret it as pervy and a child protection issue, or at least question whether or not it is. Surely he doesn't want that?? It is what he is risking though, and I would be telling him that very bluntly.
Also, I don't think it is possible to discreetly photograph a teenager who is working out? How? Just how?
Practise saying no bugger off to your DP. If he disrespects that then you have some further issues to address.