Dealing with adult son with mental health: Parents want to share?

This pain is unbearable. He didn’t have to die. He needed help but couldn’t see through all the lies his brain was telling him. God help me

My issue is not as severe as those I am reading about but….. we have an adult son in his 40’s. He is hard to communicate with. He lives across the country from us but his work enables him to visit frequently, for weeks (or occasionally a couple of months) at a time. While he a a very good guy with a big heart he is also quite fixed in how things should be. He says things like:
Our yard isn’t as well cared for as others in the neighborhood, my husband leaves everything to me, or if he does something it’s only done half way, why don’t we get something repaired, and so on.
He is on us regularly when here about home maintenance, our relationship (hubby and me), how we organize things ( or in some cases don’t organize them), why we live with some things not working ( fan over the stove is an example). We eventually get things fix but unless something is critical we don’t rush right out for repair. It is very hard to communicate to him that we have 52 years of marriage behind us, raised 2 successful and kind children, are ok with how we relate to each other and with the time we take for getting things done. At 75 years old we don’t much care for what others think about our yard, how efficient we are, or how we act with each other. . You can’t argue with him, he’s always right. This post is because this AM we had a blow up and I just can’t take it. He will be here for 3 weeks. He says he comes so he can help us. Yet, I asked him to go to a Dr. appointment my husband about a 45 minute drive away on day he is free. My husband is having some memory issues on occasion and can also be uncomfortable after these visits, so I always drive him. First he wanted to be sure his dad would drive the car, then if they could stop on the way home at a couple of places in that area, then, if not, could they leave earlier so they could stop at the places, then eventually, it was his “off day” so he would might get up early to go to the gym and should be home to leave on time (10:15 AM). I finally said to forget it. I’d cancel what I had to do and take my husband. That started our the blow up. I usually just go with what my son wants so to avoid confrontation since I know he will be going home, but at this stage I’m just tired of putting up with it. Ended with him telling me I was passive aggressive and should look at my ego and how I respond to things, closing the door and saying kindly he wanted to give me some time to myself.
Any advice for dealing with regularly occurring differences of opinion, or dealing with adult kids who think they are right and you just don’t do much of anything right, is appreciated.

This pain is unbearable. He didn’t have to die. He needed help but couldn’t see through all the lies his brain was telling him. God help me