If what you state is accurate, and I have no reason really to beileve otherwise (except the "evil" thing--that's just opinion--qualified maybe, but opinion nonetheless), then your ex is not acting in the best interest or welfare of the children. He is actually probably breaking state truancy laws. So, there should be an agency that administrates child support and visitation in your state. In Michigan it is Friend of the Court. You can petition them for arbitration. Should be minimal to no fee. If this does not work, you can contact the local branch of your states Bar Association and request a list of pro bono attorneys. This is a list of lawyers who for one reason or another is doing free legal service (some states require a certain number of hours for all attorneys). When you pick up the list, ast the clerk or receptionist if he/she can recommend someone from the list who might be good with family law.
Good luck. Hope this helped.
Talk to friends who have been through a divorce and find out who they used. It's hard to ask about a lawyer when it is such a local question - it should be someone in your area who has worked on the divorces of people you know.