I have traveled in a Superliner H-room with three different people who couldn't climb to the upper bunk. It helps if all parties are easy-going and flexible, and can see the humor in any oddball setups. In all cases so far I have taken the floor. I like to put my head under the sink so it doesn't get stepped on when the other person gets up in the middle of the night. I try to use the thin mattress that is supposed to cover the lower berth upholstery but can't always snag it, then I fold up whatever soft stuff I can into a little padding. Sometimes I take my chair apart and sometimes I leave it together and slip my feet under it. My chair doesn't have brakes so rolls around (usually over me) if not blocked in well. This is a good reason to take it apart. Nowadays the H-room has a bracket that grabs and holds it.
The most challenging was traveling with my mother. The first time we tried to sleep feet to feet in the lower bed, and we were both awake all night. What we eventually worked out was her big scooter along the back wall, my head under the sink and feet by her bed (so my body was kind of diagonal across the room), and my chair either apart somewhere or parked in front of the toilet. This meant when my mother got up in the middle of the night, she'd step on my feet and wake me, which was exactly what I wanted because she needed help for that.
The curtains that go across the room are just in the way for wheelers. We do privacy other ways, like looking away.
So, I'm figuring you are "senior" by age, not agility, and won't have trouble getting up from the floor. If you'll need a little help, you'll want your daughter's wheelchair at the right place and height, and that will determine whether you take it apart or leave it together by your bed, or put it in the upper bunk (after you've filched the upper bedclothes). There are no grab bars convenient for rising from the floor.
The floors are often filthy and have things sharp enough to put a hole in your air mattress. So I'd recommend a cheap ground cloth (old shower curtain?). If the air mattress does fail, or goes flat before morning, or you just want more padding, then borrow your daughter's mattress and see if she is okay with the remaining padding in her bed. There is another mattress in the upper bunk but it is too high and heavy for me to get down, don't know if your attendant could manage it. Remember it also has to go back up.
I do not think you will have any trouble. If the air mattress doesn't quite fit, just bend one end up or fold a section under. If you are too tall, you may need to sleep bent. If you absolutely can't sleep, you can put a pillow on the toilet lid and swivel around to look out the window, then take a nap the next day in your daughter's bed or the upper bunk. GPS and/or scanner are especially nice looking out a night window. The Zephyr is a stunning route and it is a shame to sleep through any of it.
In RRRick's photos, The luggage is placed against a heater. You can see a little of the metal casing under the sink. Sometimes that gets hot and I have caused burning rubber smells when I thought that was a good place to put shoes. If you are traveling in winter when that might come on, I suggest being careful of your bed and body parts against that back wall.