The females certainly don't look pregnant, unless they are in their first week of gestation. I would leave them all together for now. In a week check the females and see if they are becoming more rounder around the hips. If not, there is a good chance they were not pregnant when you bought them. I would just leave the male in with them and see if he does decide to eat the young. Otherwise, it would mean isolating the male for 4 - 6 weeks till the babies are weaned. It is much harder reintroducing a male once females have young babies, the females will attack him as an intruder. So, my advice would be to keep the male in and even if he does wind up killing all the young, in three weeks you will have more babies, and by the time these are weaned or close to it, the females will be giving birth to a new batch.
One other thing, what is that green stuff in the bedding?