At age 26, you're still a young person with your whole life ahead of you. Please don't let this define you. As an example, there was an episode of Star Trek Next Generation called Tapestry where Picard had always regretted letting the "Nausicaans" bait him into a fight. Anyway, this became part of the texture of who he was. And for you, too, this may have given you certain maturity or life experience or something else that you can view as a positive.
And what I'm going to suggest next is not going to help anything with the right now, but as far as medium and long-term: Give yourself the gift of considering medical school. Yeah, the real thing, getting an MD and becoming a doctor. It is a gift to yourself just to consider this. It opens up other possibilities of doing big significant things. And the ironic thing is, Macy's or Target or wherever may have their goody two shoes rules and no reason to change them because they have plenty of applicants. Whereas for medical school, college grades and MCAT are the coin of the realm, and a solid applicant (which for medical school is pretty close to all As), I kind of have a feeling, they might be able to overlook pretty much. Now, if you actually killed someone, that's a mistake that's hard to move away from. But anything short of that, it's in the past, you're now a lot more mature, and the medical college might be able to overlook it more than an entry-level job (ironically). Don't you be the one to exclude yourself. If you can find a low-key way of calling and asking them, it might surprise you.
Oh, yeah, the age thing, when I looked into medical school back in 1992, they told me they do not practive age discrimnation and that the oldest incoming student was 42 years old. Well, that gives you 16 years to take the required courses entirely on your own terms! Seriously, read "Becoming a Doctor" by Melvin Konner (1992), or the more recent "Every Patient Tells a Story" by Lisa Sanders, and as much other good stuff that actually tells what it's like that you can find. Don't sell yourself short.