Custody fight or work it out.

Unfortunately, unless the child has been in Colorado for six months prior to any action being filed, the Uniform Child Custody and Jurisdiction Enforcement Act requires that the action be maintained in Missouri since that is the child's home state. If the father dropped the suit, you could reinitiate it when the six months started but that doesn't sound like a viable option. In my experience, you are looking at a relocation custody battle. Look at the local statutes and (if they have them in MO, the family law rules) determine what the court will look at in matters of relocation. It may be a pretty high burden to get over to win the battle. Some things that the court considers here are:

1. Motivations in the relocation (did you do it to frustrate parenting time to other parent or for better opportunities?)
2. Detriment to the parent-child relationship (was he getting every other weekend or closer to equal parenting time? the more time he EXERCISED, the more detriment the relocation will have.)
3. Benefits to the relocation (better schools, closer to family, job relocation, nicer house...what caused you to move?)
4. Does he pay child support? (I know you said he doesn't...this is not a DECIDING factor but it can certainly make an excellent argument for relocation if he's not paying, you're struggling and the new location offers more money)

There are tons of other considerations. If you can't find ones for Missouri, interview lawyers over the phone and pick their brains. Ask them what kinds of things the courts consider and ask for what statutes they refer to. They should at least be able to point to a certain title of the statutes. I can't think of the exact one here, but I know it's in the ARS 25-400's.

Good luck.