I have no legal expertise but the one thing I would NOT do would be pick up your daughter and be arrested. That doesn't seem like a good idea at all. You don't mention what it was/is that you were/are using to "make the pain go away". What kind of pain? Mental? Physical? Overwhelming despair? The suggestions just given for different treatment programs and asking Salvation Army would be a good start.
Perhaps your mom is backing your ex since she's "been sober for a lot of years" and understands the dangers of whatever it is you are using. I'm only guessing cause I don't know. The first thing to do would be to investigate ANY kind of 'treatment' for your physical and/or mental problems. Just look in the phone book, ask your doctor, ANYTHING to get yourself the help you realize you need.
As far as getting back the trust in your abilities as a father, that will take some time, as it was pretty 'wild' to leave so many messages that were probably threatening to her. I don't know how old you are, or how old your daughter is, or how long you were married and how long divorced. There are a lot of factors at play here and you're going to have a lot of work to do, on yourself, before you are considered a 'safe bet' where your child is concerned. I would start by looking seriously into the suggestions made by nandm. Start with that. Network with anyone and everyone for treatment, counseling, whatever it takes to get you back as a healthy person.
I wish you the best, but I hope you realize you've got a lot of work to do. Do it for yourself, as a human being, a father, a son. You seem to be very sincere. I hope you can find it in yourself to reinvent yourself as a clean and sober person. You're worth it and so is your daughter.
:ghug3