From reading your longer post, I think you sound like you are both in the rut that so many people find themselves in at that time of life. Children and parents eat up all your time. Life is never fun, always gruelling, always pragmatic. You start to look for an escape - he thinks it's a quieter life in the country - you think it's splitting up. In that respect you are both wanting the same thing but coming at it from different angles.
It is hard but essential at this time of life to claw back some time together as a couple and learn how to have fun together again. Book a baby sitter at least once a week and do things together that you used to enjoy. DH and i started going to gigs together and then the theatre, We'd stopped doing that for years - no time, no money, SEN DS2 couldn't be left with sitters. Then we decided we'd risk it - risk the expense, risk a sitter having trouble with DS2. We found a couple of sitters that just 'got' him. We found ourselves chatting not about DC and parents but about great gigs, plays we'd loved, what to do next. Gradually our life as a couple returned.
It also helps to have some fun domestic projects together - redcorating or taking DC out for the day.
Be sympathetic to him feeling ground down. Be supportive. He sounds like a nice bloke. He wants out of the rat race, so why not surprise him with a family day out into the country or to the sea. Take warm clothes, blankets, plenty of hot soup and hot chocolate. Go somewhere nearby. Have a couple of hours fun. Pile back into the car playing his favourite music out loud. Doing stuff like this for each other shows love and respect and creates joy.
I do that for DH. He does it for me. We feel like a team. I grind my teeth at living in the country. Next thing I know he has organised a day out in London. He feels hemmed in, working from home. I put together a picnic and boot him out of the house on a work day for a wlak in the woods at lunch time. Just...put a bit of effort into appreciating each other, being interested in each other at this stage of life, making short and long term plans to have fun together. fuyn is way underestimated in marriage. It keeps marriage alove.