I've practiced this a lot because I got a handicap placard for my car very on: you have to learn to just say "fuck off" to people. I'm always on edge when I park my car or take out my cane or anything, ready to fight. Maybe that's the latina in me >.> Seriously though don't worry about it. People are rude any way you slice it. I went to a tattoo convention and a ren faire in a wheel chair and if anything I was yelling at people to get out of my way. As for sitting, compression stockings are a must. I've also been recommended an abdominal binder but I had gastro problems so I find them hard to wear. If anything the blood should pool mostly to the bottom of your torso and won't have to work as hard to get it through your whole system. Plus in a chair you don't have to worry about the standing up and constant changes in posture

Honestly, people being ableist is their problem not yours. If it makes you feel better to wear a brace as an outward sign of pain then do what helps you feel safe. However, this is unnecessary. You don’t owe anyone an explanation. Disability, and the need for accommodations doesn’t have a “look”. I personally love using my wheelchair. I also have POTS and cannot walk much and the blood pooling is terrible for me but it’s not as bad in my chair. Also compression stockings are good for this as well. You deserve to utilise what helps your health! Best wishes ❤️

Do what you need to for your body, worry about other people later