Autism and split custody...How do you???

This is Bitchfest 2012. lol My 7 year old Autistic son has recently started seeing his bio father after 8 months of not seeing him. He had him for a whole 30 hours!!! My son came home acting like a complete bear and telling me and my fiancée of two years that we were bad and he wanted to go back to his Dad's house. He also is already calling his Dad's new girlfriend "Mom." I am very hurt by this. My son has came a long way since he stopped seeing his father 8 months ago. He is FINALLY eating and somewhat talking after 7 years. We have buckled down and worked with Tyler and gave him the routine and "normalcy" he has needed but never had all his life. We have both worked hard and long to get Ty to the point he is now. His Dad came in and in 30 hours seems to have demolished the relationship we have with my son and his father is obviously working towards brainwashing my son. How does someone deal with all this drama and keep their son on track without going insane???? I am ordered to let my son see his bio dad but his Dad is already tearing us apart and this is only the beginning!!!!! Let alone how I feel about my son calling his g/f "Mom." You don't walk in and squash the title I have just been given (Since he just learned how to talk he FINALLY calls me Mom! Yays!!!!!!!!) She didn't put all the blood, sweat, and tears, into this child for 7 years. She has NO IDEA. I am thinking a lot of this is just pregnancy hormones running wild. But I do have the real issues of my son regressing because his Father is letting him get away with everything and not controlling my son. His Father has never participated in any kind of behavioral programs with his son, nor has he ever wanted to be involved with anything to do with his son until my fiancée' came in the picture and started to get close to my son and working with him. Then all the sudden...he wanted to be a part of his life. This is all so overwhelming. A part of me feels as if it would be worth jail time to keep him away from his so called Father. Grrrr...Thanks for listening!

I would bring up mediation and maybe meeting with a therapist to develop a routine and a plan, a place where you can voice concerns.