@ScottinIowa, I think you've heard just about every possible way to make her flight
less terrible but I think the real point here is that your expectations for her to fly and her not being comfortable with flying are colliding head on. To her it is pressure, mega pressure!!! You gotta let it go and slowly let her actually want it...and that may never happen. Not sure if she has any favorite hobby or routine, but if she does I'd be darned surprised she dropped it for you. So maybe this MAN up time.
Now I don't mean divorce or treat her crappy. Actually instead, be confident about flying. You are gonna fly. You might take up friends and family and even do an occasional trip. She will see that you are having fun and actually relax. At the same time she will either end up comfortable not going with you or start to want to be a part of it. Along the way, always make sure she is invited and welcome. In other words...remove all the pressure.
Regarding being pressured. I love scuba diving. When we met, my wife indicated a interest. On our honeymoon I took her snorkeling. It went so-so. So we tried just snorkeling again on another winter trip. Once again so-so but maybe worse. I could tell scuba isn't here thing. But she knows I love it and never gets in the way of me going on a trip or diving with friends. She seems happy sitting on the beach while I dive. At the root of the problem is that she does not want to put her head underwater. Period. When it comes to flying
right now your wife does not want to be anywhere near that plane. There are ways to address it. I hope you can find one of them. But pinning your happiness on requiring her to be a part of it is actually asking her to put her head underwater. Image yourself in the same situation (eg. water, heights, etc). What would you want...
If it helps any my daughter (now 10yo) became a bit reluctant to fly. We tell her "Look out the window". Doesn't help. I have her sit up front...kinda helps. I ask her to fly...kinda helps. We go on a trip...HELPS!!!! But it is always there. One thing she has locked onto is the smell. The prior owner had to burn MOGAS and I think when it leaked or something it now forever has "plane smell" as she calls it. Maybe all planes smell. But she says it bothers her the most. So I am working on that next. So getting in a plane can be more than just the fear of dying, or locked in a tube, it can be other inputs you may not be thinking off.
Good luck, I can tell you want really badly for this to work. I actually believe you'll find an answer but only with patience and not pressure.