As a general point, I know of several men whose mothers left - and every single one of them is an emotionally retarded adult, resulting in poor quality relationships with women, a tendency for inflicting pain on said women, poor relationships with their daughters and zero emotional intelligence.
It's almost as though they have no "female" side at all to them. I've noticed with these men that they are at their happiest when in the company of other men - and feel quite threatened by intelligent, assertive females - almost as though it forces them to challenge their mindset that women are not really worthy of respect.
Whilst I profoundly agree that as sentient adults, we can choose how to behave and many people consciously reject the behaviours we saw in our parents and vow never to replicate their mistakes, to make that vow means actually acknowledging that there is a risk of replication.
I often think it's different for some men.
They tend not to even acknowledge the mother separation as being the root cause of their behaviour. The only females they are close to are romantic partners and since they are women, their opinions don't count.
They value men's opinions above all else. They don't talk about emotions and feelings and surround themselves with the type of men who are equally emotionally retarded, if not for different reasons. Consequently, no man in their life has ever gently pointed out to them that their behaviour might be rooted in childhood distress. They wouldn't ever make friends with such a man anyway - and he would be regarded suspiciously by emotionally retarded men and their cronies.
The only thing than can break the cycle for those men is some really fantastic counselling, with an emotionally intelligent male counsellor. This can produce fantastic results, but of course trying to get men like this to a counsellor is akin to achieving world peace.
Ring any bells OP? Worth a try?
And incidentally, just because Relate didn't work out 4 years ago, it doesn't mean you can't try counselling again - wonder whether it was a female counsellor and therefore judged to be not worthy of respect by your H?
Relate aren't the only counselling organisation either. There are some marvellous private practioners. And if he won't go, there's nothing to stop you going.
Please don't dismiss counselling out of hand - if you've decided to stay in this marriage, I think your mental health depends on it.