Our loving black pit/lab is all of a sudden showing signs of aggression towards kids!! PLEASE HELP

by Elizabeth J.
(Small town Texan)

We have had a black lab/ pit bull for about a year now. He has been the best dog to my husband myself and our two young daughters. Recently we our husband has been deployed for a while and it is just my daughters myself and Roscoe (our dog). I might add that my husband was the closest to Roscoe but we all love him. My husband has been gone 6 months now and we have very recently moved in with his sister and her teenage son. They have a teacup male Yorker but there does not seem to be an issue there, they mainly just ignore each other. Here lies the problem since we have moved in roscoe stays outside in the yard while we r away from 7am to about 6 pm which he is not use too but he is not potty trained and tends to chew when left alone. He has more rules at this new house as in he isn't allowed on the furniture nor in the kitchen. He isn't mistreated but where he had free range in our old house there is more discipline in this new house. Since we have been here he has bitten 3 children my daughter included for no reason at all. One child walked up calmly to pat Rascoe and he bit her arm. My daughter was trying to love on him like always and he growled and bit her arm. And the teenage boy was simply walking by with his play gun to go outside and the dog jumped up took the gun and bit him. Now his bites are not hard enough to draw blood nor break the skin and he doesn't continue to show aggression after the initial snap but I still have to put the safety of the children first. I know for a fact he has not been mistreated unless u consider verbal discipline misteating. He barks constantly while outside until someone gets home to let him in. So my question is Is there something I'm doing wrong to make him this way because he has never acted aggressively before or is this just something that happens with his breed. Basically I need to know if there is something I can to to prevent this or do I need to find him a home. I am afraid one day his aggression will get worse and a child will be severely injured and I cannot allow that. PLEASE HELP IM DESPERATELY TORN?