Dude! I feel your pain!!!!!! I am in just about the same boat. I have two kids but unfortunately, I do not have joint custody YET. Everything is my fault....even after 2 years! Check out my posts and you will probably laugh at the similarities of our sitch. My EX left the marriage and it was full speed ahead for her too to be D'd ASAP. So....needless to say, same deal here. I have had my wages garnished too even though I was paying her on time and blah, blah, blah. To this day, it was my fault that the M failed and that I didn't try and too little too late...etc.
Now, as far as the two of us making JOINT decisions, that's a crock. If it doesn't work to her advangtage, it don't happen. When I am supposed to have my D14 or S16 on the weekend, she NEEDS to know by Tuesday about the plans. And, even then, she may not let me have my kids for HER own reasons. My kids know the truth and that they know that when it doesn't work for their mom, she drags out the paperwork and sticks it in their face to tell them that it is her right.
My D14 is having the most problems with her mom and her mom thinks that she needs to see a counselor and that she is lashing out and that I or my Mom has something to do with it. I told my D14 to go! Go and talk to the counselor (military). I told her that she could tell the counselor anything she wanted and that it would probably help her to talk to someone that was not bias towards either one of the parents.
Long story short.....it will always be your fault, just like after almost 2 years of being D'd, it is still mine.
Keep talking here and spill your beans, but stay supportive of your child.