I think there are several questions here. I think the most important is whether ex-wives are ever jerks.
1 . Yes, ex-wives occasionally act like jerks. It is part of the cost of having an ex-wife.
2. No, it is unlikely she can actually take your visitation rights away without a very good reason (i.e. if you abused your kids, or had an obvious drug problem she may be able to convince a judge you were too much of a risk).
3. Yes, you should talk to a lawyer.
Did I get all of the questions?