This is a great thread and while I haven't read all of it, I wanted to add to it. I just posted this in a different thread and posted about walking in the tips thread, but they both fit here, so I'll repost the basics of them.
Turnstiles can be a problem for bigger people, however, just mention to a CM that you need to use the wheelchair entrance and they will let you in that way without blinking an eye. No comments or looks. This is especially helpful at The Haunted Mansion where we asked to use the handicapped entrance and went right in.
The other tip is for walking problems.
I am a big guy. Short and stocky and dense.. like a dwarf from Lord of The Rings

Walking used to cause me several problems.. leg pain, knee pain, lower back pain. Plus, I ripped a tertiary muscle in my calf that didn't heal properly. After two hours of walking, the pain would start. I invested in a pair of Sketchers Shape Ups Sneakers. My "walking life" has never been better. (yes, they're expensive, but I liked them so much, I have bought 3 pairs) The Sketcher's make you have a more smoother and natural walk. There is no jarring when you put your heel down. I've spent all day walking through
Disneyland with no problems.. and my calf muscle healed in short time. The have sneakers and open toe sandals if you want to go sockless in the summer time. They're a little weird, at first, as you have a rolling gait instead of a hard step, but once you get used to them, you should find them much more comfortable to walk in.
My sister is a big girl and she's had knee surgery. I finally convinced her to try them and now she loves them, too. They don't really make you lose weight, but they DO tone up and strengthen your legs. I can even last longer in regular shoes now. (Note: they are not meant for any activity but walking - do not try dancing in them!)