I do know that insomnia is quite common among abductees. If he was having this sort of difficulty, and is taking a sleep aid, this might explain why he is not dreaming. I hope he can get a handle on this. Doctors say that without sufficient REM sleep, we awaken tired, our immune system suffers, then everything goes haywire. Besides, it sounds like he is missing out on some pretty interesting dreams.
Anecdotal information is that hybrid females do have sex with male humans.
If this is true, then I would have to assume that they do not engage in this activity simply for recreation or as an educational experience. There must be some function and purpose. In nature, when we crossbreed animals such as a horse and a donkey, the result is a sterile mule. I have to believe that alien knowledge and technology would easily overcome such an obstacle. In short, It does seem a logical goal, if aliens are bent on producing a hybrid species, that it be self-replicating.