OP, are you me?
When I met DH 26 years ago I was (and still am!) 10 years older than him (he was 22). His family immediately decided that I was 'posh' - they actually said that - despite my growing up in a mining village and being the daughter of a single parent who often couldn't afford to feed us. Also my age was an issue, despite FiL being 12 years older than MiL.
His parents were controlling and both emotionally and physically abusive (I often saw his father hit him) so them pretending they cared about him by advising him against our relationship was ridiculous, it was just another way to control him. When we got married his mother initially refused to come to the wedding - she eventually relented but turned up with unwashed hair, dirty clothes and a scowl, despite usually being meticulous about her appearance. She told DH immediately after the ceremony that when we split up he could come home, if he'd learned his lesson.
We limped on for a few years until it became untenable. I tried everything to build bridges - invitations that were literally laughed at, attempting to include his family in things to no avail. Eventually I told DH I couldn't cope with it any more. He seemed relieved and immediately said right, we've tried and tried, that's enough now.
He too severed contact with his wider family and all his friends for similar reasons to your DH. He has never regretted it.
Over the years I tortured myself by thinking exactly the way you do, OP - if he hadn't met me, would he still have friends/family? We have no other family or friends between us so it has been difficult, particularly when DC came along - no support or, more importantly, other people in their lives. But if it hadn't have been me that was the catalyst for DH going NC, eventually something else would have been.
Ultimately he made the choice, as did your DH. You are not abusive and you have made a lovely life together. Please stop torturing yourself.
All the best OP 💐