Change in custody and support

I divorced my ex because he was abusive to me for years. I went to college and worked part time after I got him out. He took
most care of the children because of my time constraints. Our final divorce we had joint custody with no
payment of child support either way. I have graduated and relocated for a better job. I flew the two older
ones out here for a couple of weeks with hopes for many more visits there and here. Now he is suing for full
custody with no visitation for me and wants half my paycheck for support plus transportation expenses,
medical, dental, eye, orthodontic, child care and other extraordinary expenses and his attorney expenses
paid by me, and he wants all four exemptions on the four kids. He makes more than twice as much money as me and it would leave me with 1200 a month and he would have 5378 a month not counting additional child care he is asking for and medical and travel expenses. The
children would prefer to live with me but they are afraid to move out of state. I am broke after moving and I
am supposed to answer my summons next month. Any help or advice out there? He is in Washington and I am in Colorado for two months now.

In the original order.. who got phyiscal custody ? Where are the kids living now ? What is his reason for NO visitation ?

Originally I had physical custody but after two years of full time college and working part time he was taking greater care of them and we came to an agreement for joint custody
He does not give a reason for no visitation. He just states I am not allowed to take them out of the state, although before I left he said they could visit often. I could see them if I went there but if he gets that much money from me I won't be flying anytime soon.The kids are living with him now because my lawyer told me it would cost me about 15000 to fight him, it cost me 7000 to get a divorce from him. I thought the children and I could have monthly visits and maybe they would desire to come live with me and before I left my ex said if they wanted to they could. Ages 9, 12, 13, 15. I never would have taken this job if I had known he was going to pull this kind of maneuver. I still owe the moving company for my stuff being moved here and have no more money left and owe plenty and am still paying mortgage and rent here.