So alone

How much time do you spend together??
It could be that you both need to take some time out to enjoy being without each other, if you have friends and he has friends make sure you each go out solo with said friends, or failing that just go for a walk to a nearby cafe/library/museum etc., treat yourself to a coffee and cake or soft drink, whatever floats your boat. Then when you both come home tell each other about your day. Is good to share something the other doesn’t know about.
But arguing can also be a sign that maybe something isn’t right health wise and one of you is more tetchy due to feeling below par physically or mentally. Nothing wrong with a check with he GP to do bloods and check BP etc.
As for discussing how he feels with your daughter, perhaps he just wants another person’s opinion, and is better her than the next door neighbour, am not sure it indicates he is trying he to get her to take sides, the easiest thing is to ask her.

Shimmer I feel for you both, you're in this circle now of snapping at each other and I do agree with Falling Star. I would try as much as you can, walk away when he has a go at you and take time out. Difficult I know I would find it hard nit to have a go back but you have had more than a lifetime together so know you cannot give up on that. You both need to agree to discuss things and not hide behind being snappy as it will be the norm, not good for anyone.

Great advice from the last two posters.

Get out and do some things either on your own or with a friend or another family member.

Men are ridiculously dreadful when it comes to discussions around emotions and/or relationships.

Good luck

Do you find that he criticises you and you then find something to criticise him about? Which is what happened to us when our marriage broke down. If he won’t talk about it could you both, perhaps, write down why you’re both unhappy? It’s very difficult to see things properly when you’re actually in the relationship. I’m really sorry that you’re going through this. The strange thing is that I get on really well with my ex husband now and we’re good friends. I can, however,understand why I found him so difficult to live with. He used to talk to a family friend about me and the weird thing is her marriage was the first one in our peer group to end in divorce. Was there a particular event after which things started to go wrong? It’s sohard to understand how you can be so close to someone for so long and then find that they’re almost a stranger. Maybe you both need a few days apart sometimes? My partner was driving me nuts recently ( we don’t live together) but after spending a few days apart a couple of times we now seem to be muddling along quite well again.

Is he going through a belated middle age crisis?, suddenly realising that he is in the last quarter of life?

DH has got very tetchy with everyone since his serious and complicated heart problems developed. I think the tetchiness is part and parcel of his illness, I can shrug it off if it is me, but he does it to other people and I have to keep stepping in when he is getting unduly ratty with other people for no good reason.