What these girls are feeling is unhealthy and obsessive. They're victims of molestation and harassment that have never been able to trust men before, and then when they were about to be raped by a man they were saved by another man, who is now the sole man in their entire life that they have been able to trust and rely on. Because of this, they've developed an obsessive level of sexual desire for him. What they are feeling for him does not come out of a place of genuine love, but rather trauma, emotional repression and primal mating instinct.
The correct way to go about this situation from his perspective is to encourage them to see a psychiatrist for a minimum period of time, 6 months at least, to process their trauma (both recent and past) and how it's influencing their feelings about him, the man who saved them. At the same time encourage them to exercise and train in martial arts so that they can gain the ability to defend themselves physically against men, like they weren't able to last time, so that they develop sense of control and power.
While they're getting therapy and addressing their own issues, keep a platonic amount of distance between him and them. Tell them that if they are able to commit to the therapy and martial arts and achieve balanced mental states, he will consider responding to their feelings, but so long as they are in an unstable, obsessive and post-trauma state of mind he will not entertain their advances even a little bit.
If he goes on his current path and has sexual relations with them, he will be taking advantage of their unstable mental state and building a shallow and profoundly unhealthy relationship based on a foundation of pure carnal impulse. Such a relationship is destined to end in pain and suffering for both him and them.