As said, get legal advice.
There shouldn't be any way that your ex can prevent you from regular contact with your kids, you are the dad after all.
Gaining custody if a different matter. As a rule of thumb, if the mother is competent and stable, she'll get custody. The only people who can really make a judgement on this though, are you and your lawyer.
Not true. Even in the face of a court order they can stop any and all contact with impunity.


Sorry to hear that mate, my ex wasn't as bad as that.