In all honesty I struggle to comprehend what someone at 300lbs looks like, 600lbs is easy because of the TV show, 300 still seems excessively heavy, I'm about 150 and I don't think my knees would take much more there already complaining as is.
I was a little surprised by your comment about shying away from donning your 'underpants' in front of your other half after all this time.
It took me a while but like many things, familiarity normalises things, hopefully not just contempt.
I do still like to dress in privacy in the mornings so that I don't get the occasional slight air of 'do you really have to' which has long since stopped at night, but I can now apply cream and disposable, whether plain or patterned, add plastic pants and still carry on a normal conversation without a red face.
I suppose after almost 50 years we know each other well enough to have got over the 'magic' and be comfortable with the reality.
At this point, I think I'd be happy with what's called a "staycation." Ten days or two weeks at home of no phone, no internet, & diapers sounds pretty good.