Here's some of my own personal thoughts regarding your list.
Weeing is surprisingly easy to get use to. The other end... not so much. Personally I wouldn't consider doing it without a daily release.
A problem with almost all belts, especially at first. Your pelvis is designed to tilt and unfortunately many belts prevent this, so it might fit perfectly standing up, but it becomes a problem when you sit. This is why I prefer cable belts, but these have their own issues. I carry a small bottle of latex oil to prevent chafing. You can get used to it, but it takes many months (if not years) and you often need time out to let your body heal.
Maintaining your physical and mental health is more important than remaining belted. Always ensure you can take whatever time out you need for this.
I feel sexy AF in my belt and wear dresses much more than I ever used to.
No. Just no.
Keeping hidden in general
Not so hard with a cable belt. I wear mine with yoga pants.
Pool party/beach what do you do?
Problem! I have considered wearing it at the beach, but haven't worked up the courage to get it out in public.
You need a supportive, understanding key holder, not a sadist. (And access to an emergency key if required). This doesn't mean you should get out whenever you want! But if it's 40°, get it off and go to the beach, because... well... life.
Emotional, submissive impact, not feeling free, having a thing on your body you can't remove
Part of the fun!
problems at security check
Yeah nah. You take it off (or you will be making the news).
Well you can, it's just... different. Your sensuality is heightened in many ways.
If it is impacting your development, stop. You need to own this. It is YOUR body. No ifs or buts. Do it on your own terms.