Sex workers? That’s quite the leap there.
What the OP has said is that she found transsexual videos (containing images of him) and adverts on his laptop. The adverts were to meet people in the woods for sex, and for photo shoots with no location specified. She then clarified that some of the videos were taken in their bed, though not all.
In my experience of amateur porn, it overwhelming involves just one person, usually having a wank, particularly if filmed at home where the person involved doesn’t have sophisticated recording equipment. Clearly, I have no idea if this is the case here, I’m just going on experience.
Even where videos include two or more participants, and again in my experience, the people involved are usually very clearly amateur and filming for personal enjoyment not because they’re sex workers. I’m sure there are exceptions, but the most likely scenario is that the STBXH has found and met up with likeminded people for his sexual kicks. I accept that the videos and trans content are uncommon, but my no means unheard of and certainly not illegal.
We have no reason whatsoever to believe that the DD was in the same building when the videos were recorded.
Unless the OP tells us otherwise, there’s still nothing in anything that she’s posted which puts the DD at any more harm than either parent meeting someone and bringing them home for a ONS - actually, she’s at less materially less risk if the STBXH is ensuring that any sexual activity in the home takes place when she is out.