I don't think they would view a 4th marriage as hugely different than a 3rd marriage......and a 3rd time bride, previously committed to a mental institution, is who you chose to be the mother of your dd. Because of that, I believe that making a big deal of her 4th marriage could actually lower your credibility in the eyes of the court.
I have not been through the process yet myself, so my opinions are just that.
I would hope that you will be able to block your ex moving a great distance away as the CP of your dd because such a move would affect your dd's ability to keep the same close relationship to you, not because your ex is a nutjob.
If your ex's new (repeat) hubby moves to your area, I believe you should have 50/50, at least.......because that has been the status quo, not because you don't like your ex's choice for #4.
Is your ex currently also in Kingwood, TX ? How far is that from Dallas ?