I've learned the hard way, it's not a good idea to get between a spouse experiencing some form of MLC, or just simple WAW selfishness, and their dearly held dream of how things should be. Their hearts are cold. And somehow the spouse becomes the reason for everything bad in their lives. They all say it. They tend to do the same things, too.
You single best chance at turning things around is to focus on you. Be busy, be happy, work on things you can change - you'll be a better person for it, and it often turns a bad situation around. It makes no sense - but it works.
A lot of the guys here really learned a lot from reading the book. I see them recommend it to one another all the time, and comment on how it helped them learn and grow.
Another tip I've learned is that the sooner you stop watching her to see if she's noticing your changes, and just focus on yourself while still being pleasant to your spouse, the better off your frame of mind will be. The goal is to become a person only a fool would leave.
My key words for myself are strong, calm, and pleasant. It takes some effort with your world crumbling around you, but once you master it? Change begins to occur. All situations are different as far as what change, but the changes in you will be worth their weight in gold! You'll find that you're more peaceful, happy, and calmer in general. Absolutely priceless.
Update and let me know if the book was helpful for you, too. I suspect, from all you've said - you're definitely a nice guy...sometimes to your detriment.