OK, so things are a bit clearer for me now! I think that by accepting his relationships from a dating poly perspective, there has to come a time where you let go of the fact that they will have sex. These are intimate relationships that you are aware he will pursue.
He has been honest with his intentions and, as long as your health is not at risk, this is an expected next step I believe. It would be hard for anyone to maintain a relationship with indefinite celibacy in this instance. That being said if the other women's partners also have issues it will have to be negotiated on their end.
If you are not comfortable with the inevitable sexual aspects of his poly relationships with others, than again you might consider finding a more fitting partner for yourself.
It's ok to let go and keep his friendship. If your heart is not in this it will tear you apart.
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
Poly Events All Over