OK -- I've found tubes that will work. As for the tire: if I currently have a 26 x 7/8 (aka 22.2 mm), would 26 x 23 work? I'm not finding any 26 x 22.

Also, what are "steel" vs "folded" tires?

I do have a presta valve. As for how I went through 4 tubes this week:

1) tube #1 (came with bike; may be original from 2007?): presta valve malfunction while topping off -- couldn't get the pump head to seat deeply enough. Something appeared to be wrong with the stem (the part that screws). It wasn't "as high up" as the other one. So I put on...

2) tube #2: my first changed tire ever. I pinched it with my lever putting the tire back on. Multiple holes. Unpatchable. Won't do that again.

3) tube #3 finally worked and we completed our ride in record time. But, I went to top off my tire this morningand somehow, the entire little stem vanished! So now I am on...

4) tube #4.

I clearly have some more learning to do, but at least I know how to change a tire now! I'd been quietly dreading that for a while... I knew the workshops I'd gone to where they change a tube in 5 seconds made it look deceptively easy!