Ugh. I have joint custody and he has visitation every other weekend and once per week. He does not exercise the once per week visit at this time. It is in my divorce decree that my X may not drink in the presence of the children, nor 24 hours before. Unfortunately, there is no monitoring, but my children are older. I would absolutely at least require Sober Link monitoring so that he still has to blow during the visitation. Sole custody is very hard to get, but I have learned that it really does depend on the judge themselves. I would have a local attorney who knows the judge and knows the ins and outs of what to expect w/that judge and prepare accordingly.
My heart is with you.