Come back when you receive your score since that can cause things to greatly vary.
Volunteer Peer Mentor sounds more like non-clinical volunteering if you were not seeing them in a healthcare-based setting. Contributing 200+ hours at the homeless shelter would help you in light of the DUI. If there is a professor you are close with who is aware of it, it could help for them to speak a bit on your behalf regarding it as part of their LOR. Your grades are fine, so I do not think it would make sense to bring them up.
If you find out that you can expunge your record ahead of time, do that and verify with legal experts + background checks that it will truly be off. Do note that some schools will still ask and want to dig deeper in their secondaries compared to the AMCAS process.