Abuse is a touchy subject, especially to those who have endured it. If he truly was abused, only he can decided when and most importantly IF he wants to deal with it. As it is with alcoholism, when he decides he needs help, he will find it. Until then, trying to help him get there sooner than later will only lead to problems, and resentment towards you.
Of course he was abused in some way by his A parents... he abuses you, right? Mentally physically, emotionally, whatever the type may be, he learned it from somewhere. Probably the parents.
For whatever reason (everyone has different backgrounds) it is ingrained in us to try and help. to try and fix things. Try not to be so hard on yourself when you slip back into the codie mode... it took a long time for you to get this way, it's probably going to take a while to change it. It's not a light switch, you can't just turn it off. Be gentle with yourself, at least you recognize that you are doing it!