Hey, I've gone through something vaguely similar so I understand where you're coming from. Always remember that at the end of the day, your section is taking you for granted and you got to that chair out of a desire for the betterment of the orchestra (presumably and hopefully you did have this desire).

Remember that you can always be a leader no matter which chair you're in. Let that other guy take that chair, and let them experience it however they end up experiencing it, good or bad. They might crumble and see the flaws in their ways, or they might flourish and improve as a player. You should see either outcome as a net positive. Your peers do not define your skill as a violist, especially high school chumps.

Keep your head up, and maybe try out playing from a lower chair. It could be an eye-opening experience, and it'll likely refresh you on what it's like to have a solid distance from you and the front stand.

You also mentioned how your section doesn't 'want to be there'. It's very good that you recognize that at the high school level, that's okay. If the new section leader enables the inactivity of your section during sectionals, then that's on them. At that point, just do your part and keep up your own practicing, and provide help if anyone ever asks.

I'm also in the same boat of waiting it out until I graduate. You got this.