Gestation is usually around 3 weeks, 21 days. If your male is killing off your pups, you do have a problem. Most likely if you feed him off and try to introduce another male the females will kill him. If you take him out and put him back later, the females may try to kill him, and/or he will continue to kill pups as they are born. Mice are just nasty critters. You have a couple choices.
Kill him, buy a new male, clean EVERYTHING~ hope for the best (if you have the time and space this is more likely to work if you seperate the females into seperate tubs ALL BY THEMSELVES (one female per tub) for a week, then put the colony back together with your new male and all your females in a CLEAN tub. (I don't have the space or time to mess with that~ but it is more likely to work if your females are confused)
Leave him, hope he stops it.
Buy a new male and three or four new females. When they start producing, kill off your first colony (in the mean time, pull the pinks as soon as they are born so you can use them as food for snakes rather than the sire)
Kill off your male, hold back the pups that have already been produced. Keep TWO males and a few females of those pups. When the two males are about 3 weeks old, cull one off (you only kept two JUST IN CASE one of them didn't make it to adulthood) Eventually the male you kept will breed your original females and his sisters for you~ and is somewhat less likely to kill pups as he will have been brought up in the colony. (this is what I would do, but I keep a lot of rodents, so I can afford to have a slow start on a colony.)
Good luck!