Stepparent adoption in CA - new here

Hi, I have been reading through all the posts here over the past few days and decided to register today. Long story short.....My son is 11 years old and last saw his bio father in 1998, not even a phone call at Christmas or a birthday card. My ex didn't pay child support for years and owes $46,000 in arrears. He has been paying through wage garnishment since 2003, because he never worked before that that we knew of. I haven't had his address or phone number since 1998. I remarried 6 1/2 years ago and have another child with my current husband. My son considers my husband his dad and has called him Dad since he was 5 years old. My younger child does not know (yet) that her bio father is not also my son's bio father! I am mom, my husband is dad and they are brother and sister, simple as that. My husband has wanted to adopt my son for years but we were always under the impression that we had to be able to personally serve my ex, so we never did it (I could kick myself). We had moved in 2002 but my ex's mother was still in contact with us and even used to come to our house to visit (they live several hours away). His mother used to write me letters apologizing for her son. Once she even mentioned that she would support a stepparent adoption, when we did it. However she always refused to tell us where her son was! I knew she had always been in contact with him, even though she said she only saw him once in a while. She and I had a falling out in early 2003 and I haven't spoken to her since. Out of the blue, my ex served me with papers to modify his child support amount and for visitation - the court docs were handwritten by his mother! Apparently he had a new baby with his current girlfriend and also has another child with another woman (whom he also owes for back child support). We went to an attorney and he advised us to go ahead and file for the stepparent adoption now anyway. So we did that. My son wants to be adopted by my husband and doesn't even know his bio father! (It's so wierd to say to your child "When Dad adopts you...."!) We went to court to modify the support and visitation. I was amazed that my ex showed up. He even brought his new baby into the courtroom. My ex didn't even mention visitation! All he seemed concerned about was his support amount. Since he makes much, much less than I do, his amount was lowered by about half. I was fine with it because I didn't get the money when I really needed it. Now i feel like we shouldn't even accept his money. However, he told my attorney that he will not agree to the adoption and will fight it. So, now we have to wait for his response (which he said he mailed the day before - he doesn't have an attorney). What do you, more experienced people, think about this situation? Thanks. (sorry to be so wordy)