Yes keeping everything inside for a bit can help as the semen will help keep the sperm alive if for any reason your body is hostile but eventually it will leak out

It doesn't matter if some comes out when a man ejaculates most of the sperm has already attempted to start their mission what is leaking from you is semen which is the fluid that house the sperm. Your body took what it needed to get pregnant which is the sperm and expelling the foreign fluid which is the liquid (semen)