Can I get full custody of my kids and move back home to new mexico

i raised my kids for 13 year with very little help from their dad.In 2009 my family and I were moving back home to new mexico and the night befor we left my ex said I couldn't take them. We have joint custody so I didn't have a choice but to leave them since I had no home in las vegas. since then he has been trying to replace me with his girlfriend when it comes to my children. My ex is ex law enforcement but he only did that to hold it over my head he also teaches ccw classes and becomes friends with anyone with law background so he can use them against me. He has mental abused me for years and now he does it threw my kids. He also mentally abuses our children that I myself have whitnessed. He has also allowed his girlfriend to hit my boys and punish our children as I was told by the kids and when I ask him about it he says now that I know i'll get in trouble to.The last few years he's made me pay him child support but in our divorce decree he's to pay me.Please Help me!!!