Fry will be safe until the adults are preparing to lay again. (3-5 weeks)
Other fish with a pair? My pair murdered/attacked everything apart from a male BN, if you do add anything go for fast fish like danios and have plants (plastic is fine) for tehm to seek cover in.
My female beat up my male once, they can do this if the male is ready to breed again before the female - she will drive him off quite violently. Again have plenty of hiding places and if she seems to be overly aggressive to him remove him for a few days.
I am worried though - you say you have got the Kribs but you only got the tank yesterday? Kribs in an uncycled tank will not be happy and with your current ammonia issues/overstocking issues in the other tank I am wondering where you will put the kribs?