girlonadolphin, My first marriage was a replica of your relationship (with added violence), and like you I was worried about how DS would perceived his father as he got older.
I never told him about my relationship with his Father (we divorced when DS was 3).
DS saw his Father, (supervised by his paternal Grandparents) till he was 10, by which time his Father was turning up at his Grandparents, once in a blue moon (usually because he was on a bender, with Grandparents trying to cover for it by now)
Although we lived 10 minutes away from exH, their contact became less and less.
When DS was in his 20's he decided to initiate contact with his Father.
His Father turned up drunk. DS asked him to leave (and not because he was actually drunk, DS is a rugby player, who spent most of his youth in the club after the game, so has been that way himself a few times, but Thank God does know when to say no)
His father then told him that I had turned him into a MiniMe nagging him about having a good time.
DS said no it was because he could rememebr even at three, what his Father was really like.
I hadnt needed to tell him, the residual memories where there.
Three years ago, DS got married,shortly after he and DDIL met his Father in a pub.
DS tried again and introduced his wife.
He got a torrent of abuse, because he had got married without his Father permission, without inviting him.
DDIL stood up to him, after DS stood shaking, just like I used to when I got the abuse, DDIL was not going to let it happen to DS and told ExH in no uncertain terms to never contact them again.
Please Please leave him, do not let your DS become his Fathers person to blame, he will, when he has not got you to blame he will turn to the next person in the line.
You and your DS dererve a better life, and you WILL find one.
Stay with him and it will only get worse.