High end and budget IEMs do not really have that much of a gap, I am very happy with a mid range portable setup. People paying 5K for a portable setup might as well buy a nice desktop that would sound much better.
Lol, no, not at all. If anything, acrylic might be even less durable.
You will also need to reshell after a certain period of time, which costs around $200 every time. If you want to go down the CIEM route, it might be worth it if you go for a more expensive one, I would just leave the Heir as a universal.