It just sounds to close to home for me, I can't give any advice on it but I can sure relate to it.
My gf will call me randomly from time to time, and if I don't pick up, she starts saying I'm with someone else, and is always suspicious I'm gonna leave her for someone younger... I think that's very similar behaviour to what your wife is doing to you!
Then sometimes she cries me a river, and I just feel powerless, completely and utterly useless! I hate feeling useless... how can I be expected to perform feeling useless??
I talk to her all the time, that I care and love her and reassure her. I mean I do that everyday, and I'm still doing this everyday for the past 2 or so years since all this started!
And I don't mind doing that, except for when I'm accused of something I haven't done or she starts acting weird and freaking out for no reason, then I feel like crap.
Frankly I just want her to be happy, I just wish things could be like they were 3 years ago, it was fantastic. I mean sometimes it still is, but there's a lot of annoying things in between.
It's a little selfish of me, but somehow I find a little comfort in reading about your experiences, because it makes me feel as if I'm not alone out here struggling with this crap. I wish it all works out between you and your wife. If anything I feel better for venting some of this stuff out, hope you do too!!