My DH is moving from mild to moderate stage BvFTD. I began noticing that he was masturbating in bed frequently. I've walked in on him enough to be upset though I've smiled, given him a hug, and not acted like it was anything out of the ordinary. I do put up with ugly comments about me being frigid, but I can't be intimate with him at this point. I am being very affectionate when I bring his meals and help him find or use the TV remote. It makes me sad and even a little afraid of what is to come as his disease advances.
At this point, affection on your part, if at all physical, is a mixed message to his fragile brain, that you are physically caring, but then unwilling to progress physically.
I do think that you are certainly beyond the mild stage.
This is worthy of an appointment now with his MD, you, and your spouse if he is indeed only in mild to moderate stages. There is a lot of disinhibition going on now if he is allowing himself to "be caught" in this somewhat "normal" activity.
You may be looking at placement earlier than later, but I don't think only for this problem. Sounds as those the FTD is progressing with some rapidity.