rewarding the lazy parent???

I am the divorced mother of two teenage sons, have joint shared custody with their father and pay maintenance and child support to him due to my income being greater than his. The primary reason for my divorce was due to his lack of ambition and not contributing to the family after we no longer needed one of us to be the stay at home parent- once the kids were in school full time. At the threat of divorce, he finally found a job yet I was already leaving. He has kept the same job for six years making around $10/hr and working a 35 hour week. I supported our choice to keep the family house and allow him to reside there providing payments were kept up. I ensured that the combination of maintenance and child support covered the house and his car expenses plus some. We are at the 5 year mark where maintenance expires. I have worked hard to be a very involved parent working my work schedule around nearly every childhood 'event'. I have paid for all expenses minus a few small 'contributions' from their father. I live in a transient neighborhood in a very modest apartment, yet the children prefer spending their time in their mom-home over their dad-home and the house they grew up in. He has let the house (that we both own) fall apart physically and cosmetically. He maintains the same low income, part time job even when full time hours are available. He worked over ten years prior to taking a leave to be at home with our children, making over $30K/yr and is a healthy man, mentally and physically. While I continued to struggle with the parenting/work schedule I still managed to earn more each year than the last. Unfortunately, I absorbed much of the family debt during the divorce and what didn't get absolved in filing chapter 13 (meaning I still paid a significant against that debt), I absorbed in 401K loans. With the debt I still owe on and the cost of 98% of the children's activities like hockey, school trips, college entrance exams, clothing, social- I take home less than I pay him each month, minus the 4 times per year I earn a commission which mostly goes to paying back friends I've had to borrow from to get by the previous three months. After speaking with a lawyer this month, while preparing for the next chapter- post maintenance, I learned that if I choose to keep the joint shared custody arrangement, I will actually owe him significantly more now for just child support than I do for the combined alimony and support to date. The lawyer recommended I apply for full custody since the children spend most of their awake hours at my house otherwise I face rewarding their lazy father the joy of living in a home that he doesn't deserve, and on an income that he has not once tried to improve in 6 years. I have always wanted my sons to have a relationship with their father and do the 'right' thing by the law and teach them a positive example in life. When does the law teach the lazy, indignant, selfish leeches to contribute to the economy and to own up to their social and parental responsibilities? My reward for working hard is to struggle exponentially more while my sons are being robbed of finances to enhance their lives, education and welfare because the law says their father gets to sit back in his big house and let it rot away. Where is the justice? How can we rewrite the laws to discourage such a crime against the hard working and the children? Now I must borrow again from a friend thousands of dollars to hire a lawyer to create stress and challenge the custodial situation just so I can do what is best for my children. I would be quiet and content paying something to keep peace in a broken family- now because of this law, my sons are going to be put through a hell where they must make legal decisions based on our laws where they may feel like they are betraying or hurting a parent. I never meant to see this weak man hurt, I left because it was wrong staying, yet doing the right thing is doing nothing more than rewarding lazy and hurting a child/parent relationship. I want to see this changed. Where is the justice?