How do you know if leaving is the right choice?

I've been with my husband for over 25 years was very young when I met him. I'm in my early forties, and now I just feel done, feel my confidence going and out of hope that he will change. I don't want big changes, I just want him to put his dirty dishes in the dishwasher is standing open and obviously dirty. (I realised this morning I have lowered my standards so much that I don't even expect him to empty it when it's clean to put his dishes in, I'll do that) He doesn't respect my boundaries around his smoking (eg pelase don't smoke in my car but he does). He never helps around the house but I keep passing up roles and opportunities to support the choices he makes in our business (without my consultation or even if I say no) that allows him to follow his dream but he never gives me credit for what I do, he always tells people that HE does all this stuff, when I'm in the background doing all the admin and the shitty little unnoticed tasks that allow him to do what he wants. He spends a lot of money on business decisions without talking to me first, but then expects me to sort it out and deal with the consequences of not actually having the money to pay for those decisions. I used to challenge him and voice my opinion a lot more, but it always ends up in a huge fight, with him swearing and screaming at me. I feel like I'm always walking on eggshells waiting for him to lose his temper (not physically abusive, but verbally) Now the line he trots out is that he's been like this forever and he has no intention of changing, so I just need to get over it. Which may be right. I've built the rod for my own back for being the good little wife when I was younger and did everything for him. He always encourages me to do things that I want and that he will help me more, but he never ever does, not even for a week.

How do you know if it's the right choice to walk? I'm scared it's menopause talking (I have been going through early menopause for a few years) and I will regret it later. My youngest is in final year of school, so I want to wait until that's done (I've gone this long, another year won't matter, literally been counting down for the last ten years). I look on that as a year to prepare and make sure it's the right thing to do. What suggestions do you have to prepare? He will not attend marriage counselling at all (I've tried to get him to go before) but I'm happy to try and go to some myself. I have a couple of options of where to go, I am fortunate enough to be able to stash money away. Anything you can suggest?