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