Parenting evaluations

[Focused]

I am new to all this and having given up on my son's mother EVER giving me some custodial rights, I am now pursuing mediation and preparing to file in court if the results are not satisfactory.
Basically, I am tired of my son and I being put through the ordeals that his mother puts herself through (moving from Minneapolis to Portland, back to Minneapolis and then to California in the space of 4 years). It has been almost impossible to create a stable life with him and my visitation swings on her moods. The most recent negative choice on her part was the unilateral decision to send him away for most of the summer, which I have gotten her to whittle down 2 weeks away and 5 weeks with me. I have no custodial rights and have been put through the wringer trying to accomodate her at all occasions in order to have access to my son. I grew up without my father as a result of divorce and have made it a priority to be present for my son.
I am really interested in finding out more about the Parenting evaluations and am wondering if that is a step I will have to wait for a court order for or if it can be a voluntary move. I have no intention of fighting with his mother for my rights and the rights of my son unless I must, but repeated choices that seperate he and I are making it feel like I must. Any advice on ways to seek an amicable agreement without the acrimony of a full-on custody battle would be greatly appreciated. I feel very strongly that this would be in the best interest of the three of us, especially my son and myself as his mother is extremely volatile and has threatened among other things to "disappear" if I do file in court.
Quick backround.........
My son's mother and I never really had what would even be called a relationship and I was not on the birth certificate. I signed an ROP when she agreed to let me and have remained current on my obligations (support, childcare, medical and dental etc). I feel that I would have a strong case in court, but am unwilling to make my son watch us fight and subject him to the crap. judgementalism, and anger that I observed between my parents. I am not angry, but I am tired of being subjected to the emotional, verbal and psychological abuse that accompanies the ups and downs of his mother's choices. I am hoping that she is not passing the things she says to me on to him, but as he gets older (7), I am having less and less faith that she is not involving him in her poor mental hygiene. One major obstacle in the whole ordeal is that she is working for the county's child advocates and will be well-armed with how to avoid releasing any rights. One would think that her experiences would show her how lucky our son is to have a clean and sober dad who loves him enough to do whatever his mom asks, but it really hasn't worked out like that at all. I have to admit that moving slowly forward, by filing for mediation, looking for a lawyer and doing the Google searches that led me to this site are keeping me in good spirits and, most of all, focused................

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