How successful would I be in termination of my ex spouse's rights since child support and visitaton are not being followed?

Not successful. Being a parent is a fundamental right--even if they do not visit the child or pay child support. Either the state would have to terminate his parental rights, or your ex-husband would have to agree to have your current spouse adopt your children.

If you file a stepparent adoption in Missouri, you must be able to prove that the biological father has substantially neglected or abandoned the child for the six month period prior to filing, unless the father consents to the adoption. Whether you have enough evidence under the law to prove neglect or abandonment depends on the specific facts of your case. Please immediately schedule an appointment to meet with an experienced family law (adoption) attorney who regularly practices in the county where you reside (or where the original custody/support judgment was entered). That attorney can discuss all the specific facts of your case with you and advise you on how, and when, to proceed.

Child support and visitation are two entirely separate issues. If you created a situation by moving away from the father do not expect the Court to have a lot of sympathy with regard to the frequency of the visits. Failure to provide child support alone is not sufficient reason to termination of parental rights. All cases are fact specific and no one can give you an exact answer, but simply suggest you to seek counsel in the matter.