Our HCBM has fought tooth and nail to limit my DH's visitation. DH gets 6 weeks on a long distance schedule and pays maximum CS. Before long distance, BM denied overnights for every reason under the sun.... why? CS is based on overnights. After a year in court and $30k in legal fees, we are no longer fighting for more visitation. BM tried everything to limit visitation including lying, falsifying records/documentation, false allegations, and perjury and the judge ate up every word. 

BM still emails DH about how hard it is to be full CP and that DH has no idea what BM goes through. BM also emails DH after we have a long visitation, "thanking" DH for taking SS to "share in the parenting responsibilities". The irony is that BM has SS rarely. When she lived locally to us, SS would be at BM's parents 6 days a week from morning until bed time. BM saw him on Sundays and first thing in the morning before dropping him off at BM's parents. But BM wouldnt let DH take him because $$$. Now that BM lives long distance, she relies on school, daycare, her GF, and neighbors/friends to do the parenting. SS has told us that he is only home for bedtime and spends all day and weekends out of the house with everyone but BM. BM doesn't know the meaning of being an involved, full-time parent. 

We would happily take SS full-time and want to take on those responsibilities, yet BM won't give up control and CS. It's amazing how these HCBMs want to have their cake and eat it too. 

BM's household is always more important that DH/yours. You are not obligated to pay another dime to BM outside of what is court ordered. We used to pay half of things for SS (sports, school supplies, clothes, etc.) because we thought we were obligated to. Our attorney told us to knock that off because BM was using sports and things to prevent visitation. Our attorney said: "why should you pay for something that BM is using against you?" We stopped paying extra and BM flipped out. But, BM was using CS to offset her income/expenses, allowing her to buy a brand new luxury car, pay off significant amounts of student loan debt, buy a huge house, etc. BM was using CS to get ahead, not for what it was intended for. 

Our attorney gave us excellent advice. He reminded us that we still have to provide for SS when he is here. We pay more for a 2 bedroom apartment, even though SS is never here, because it is required for visitation. We pay for clothes, toys, toiletries, activities, groceries and everything for SS in our home. We don't get CS for that, so don't keep paying more than your share for BM to be comfortable. CS takes a huge chunk out of our household income, but we still try to live within our means and not complain because we know we owe CS to SS for his needs.