As to the 17 year old and BF staying the night with her when she is at her dads I suggest you swallow hard and have the talk to her about unsafe sex - bare sex with no condom and STDs and then tell her you want her to get a Norplant or something like it to offer long term birth control and tell her if she agrees to the long term birth control once its done then its a closed subject. Getting the father to pay what he is supposed to well that sounds like you might have better luck taking bets as to when the mothrin will land with motherships hovering