in my opinion.  

Do you think he would stop saying all those things, being disrespectful, etc if you werent there?  Would he really give up on living with his father permanently?

Sounds like you are the scapegoat in this.

I would stop making any comments or voicing your dislike of Bio Dad no matter how heated it gets.  

ETITHAH

(everybody is the AH).

Yes.. you have a set of challenges.. permissive mom(and unsupportive parther).. toxic EX.. and a kid that was not "easy" to be around.  

BUT.. you have said that you have on many occasions had your own outbursts.. talked badly about his father.. and you were the enforcer in your home..  so.. yeah.. your treatment of him.. and things you have said and done.. have contributed to the estrangement.. and you are the adult.. and should have had more control.. or gotten out of a situation that had you losing your cool constantly.

I'm not saying a SP has to just eat a crap sandwich.. but it isn't your place to talk badly about his father.. your wife should have been the one disciplining her bio son.. you were doing it without the "loving connection" of a bio parent.. and that can breed resentment.. and you already had forces that were contra to you having happy blended life. and you had a hard time maintaining your cool.. I get he must have been frustrating.. but again.. as a parental figure.. we don't get to lose it on kids.

Who knows. You certainly didn't act in the best interests of the child or a happy home. But your wife stuck with you and didn't protect her son from you, your comments and your anger. So either it wasn't that bad or she had a part in  allowing this to go on in her home. Sounds like the whole situation is messed up for this child with this bunch of adults as his role models. 

It also sounds like you are now accepting what you did wrong and open about your part in this situation. So that is a positive thing.

Hopefully you are working on yourself so that you find better outlets for your anger and control what you say around others to more appropriate comments. 

Your view is clearly that there are many factors at work here and the other adults also played a part in the path to the current situation. If that is how you think why are you bothered by our validation? If your wife is holding this over you a bunch of strangers online is not going to "win" the argument for you. 

You two would strongly benifit from some couples therapy to learn how to argue in a more healthy way and to help you find common ground over this issue with her son. 

The constant need to blame you is not healthy. You two need to find a healthy way through this or it will eat up your relationship. 

FYI I'm in a similar situation with my husband and sd who refused to visit for her winter break as she usually would, supposedly because of me. My husband though is not blaming me, has not brought it up in anger and has supported me. It is possible to maintain a strong relationship through these difficult issues. 

Not the A$$hole

I'll take a stab at this because I've been where you are and it's a place called "But look at what THEY did and see how it influenced what I did."

Yes, you showed up on the scene and were handed a sh&t sandwich with a meddling ex, a toxic MIL, a permissive parent as your wife and a child who was out of control.

The MOST IMPORTANT thing I've learned in my journey of self improvement is that it doesn't matter what anyone thinks, says or does, we are each responible for our own behavior.

Yes, there are mitigating factors to consider that might qualify you for some mercy.

At the end of the day you messed up and it's not anyone else's fault. And you need to own up to it and make amends even if none of those other people EVER acknowledge their contributions to the dysfunction.

Make a sincere apology to your SS and make NO excuses. But stand by your rules and boundaries for your own home and RESPECT his decision to not visit there until he feels comfortable. Next, completely disregard what your inlaws or the ex husband think of you. Their opinions do not matter.

Finally, do better.

Whether or not you are the AH depends a lot on exactly what you said about SS's dad and the context. Hard to say without details. Did you state factual information such as "He doesn't pay child support." Or,  were you verbally abusive, such as "You'll never amount to anything, just like your no-good POS sperm donor!" 

Per your own statemnt, you likely have been TA at least periodically.

I get the anger and frustration.  I lost my temper with SS a few times over the years regarding his behavior and engaged with him in anger.  However, I made sure to not bad mouth his Spermidiot to SS. His mom and I were extremely careful about that.  Though not as careful in the first few years of our marriage as we thought we were.

When he was a toddler we always made sure to only discuss the Spermidiot, SpermGrandHag, the CO, etc... when he was not in the room. Or so we thought.

When he was about 3yo his Spermidiot called our home on one of his periodic tear fest "I still love you so much. Do you still ove me? I miss my famileeeeeeey!" pathetic crap calls to my wife.  She laughed at him, told him he should  have thought of that when was banging whatever next 16yo he could get his hands on then asked him if he wanted to speak to his kid.

She then told to SS to come to the phone (pre cell phone days) that his "Daddy FirstName" was on the home.

Happy little toddler SS came bouncing to the phone, took it from my DW's hand and said in a cheery toddler voice... "Hi DaddyDickHead!!!" His mom and I both about choked.  Fortunately "DickHead" sounds much like his actual first name.  DickHead expostulated "What did you call me??"  as DW knocked the handset out of toddler SS's hand and onto the carpet, picked it up and told DickHead "Sorry, he dropped hte phone.".Then handed it back to toddler SS who started chattering in a happy babbling toddler stream of consciousness.  That seemed to get Daddy DickHead past  what he "thought" he might have heard.

Never again did we ever use anything but their actual names when discussing them or the situation when SS was in the house.  The colorful labels we applied were only used between the two of us when SS was on SpermLand visitation. It woudl have been far worse if then toddler SS had referred to SpermGrandHag as "GrammaBitchFromHell" as DW and I referred to her back then in our conversations. Fortunately, he apparently did not key on that if he heard it.  If he had ever called her that in conversation while on SpermLand visitation she would have called ranting and flames would have shot out of the telephone.

Little ears hear everything. Even when they are at the other end of the house.

So, don't do that again.  Or.. you will CTBTA (Continue to be the asshole).

I get how difficult it is to have your life jacked up by a difficult skid who is screwed up beyond measure by an idiot opposition parent. Just do not let any of them drive  you to abandon the firm ground of the high road, or at least the appearance of you being on the high road.

Do not beat yourself up over it. It is what it is. Just make sure it stays in the past and you do not repeat those mistakes.

If what you said was factual and not rantingly insulting, you may not have badmouthed BioDad to SS at all.  Though those who do not like the facts related to themselves will claim being badmouthed when all that is said is a clear statement of the facts of their behaviors.