I agree with others about your dh getting something out of being the one in charge. I think this is a deep seated problem and you have my symapthies - when I read your bit about him doing most of the talking at Relate but accusing you of gettting all the attention, I felt really sad for you. But I get the impression that you do talk a lot to each other, and you say he is a good man 80% of the time, so it's not as bad as it could be.
Do you think your husband needs you to hover defeated in the background while he shows you what a good dad he is? That's the impression I get. Does he need an audience in other words?
What would happen if you deprove him of that audience? throw him off balance. Next time he's taking over, look relieved, say you cuold do with a break from ds and happily go off and do something else. Let him do all the changing, feeding, clearing up, getting ready - don't be around to help with the menial tasks. Rather than taking 'time off', go and do something else in another part of the house, whatever you enjoy that you can get immersed in - like gardening, cooking, sorting out the photo albums - so you are still 'working' so he can't say you have gone off in a huff and are in the wrong. You could even say you are looking up parenting sited on the internet and come on here
If you dh starts to talk to you about ds, say something like 'sounds good to me, why not give it a go when you're with him' but don't seem over interested or up for a fight. And don't say you will follow his 'rules' when he is not around. If pushed, say you'll think about them. I don't know your dh so I don't know how he will react if you do this, but I feel he won't get half as much satisfaction out of being right if no one is taking notice. If he gets angry ask him what's the matter, and listen to him - but don't justify yourself.
The other thing is, soon your ds will be a fully fledged toddler. IME That means hell for controlling people. Toddlers have minds of their own and will tell you what they want constantly. That should be interesting for your dh. Being in sole charge of a toddler for hours on end can get on the nerves of the most superdad. If he rejects your input now, he may be begging for it in six months time. Must dash but will come back...