Even though I'm not an expert but I'll give you my take on it.
1) Do I need to worry about the C- in orgo 2?
The whole purpose of the SMP is to overcome low GPA so I don't think it'd be a big deal if you do well in the SMP. (Hey, be glad you didn't fail it!)
2)Which 3 smps/master programs do you think I have the best shot at if I apply this week?
So, your professors have already written the letters for you and everything? I'd say that's the part that takes the longest. But if your application is ready to be sent in complete this week I don't think you are too late. People get into programs in may, june and even july so I wouldn't sweat it. Even if you get into a waitlist somewhere the chance of moving off of it is very high in the summer since acceptance yield for these programs are super low from the seems of it. So instead of looking at places where you think have the best shot at, apply to the places that you think you will benefit mostly from. Your stats are not that low for SMPs and won't rule you out of any. But since it is getting on the later end of the cycle, I would apply a bit more broadly.. personally I would apply to 5+.
3)Should I be trying to volunteer somewhere or shadow someone right now to help buff my resume even though there's only 1 month of school left?
So, I woulnd't recommend starting a new volunteering experience just to do it only for a month. Adcoms are looking for long, continuous commitment and 1 month might do you more harm than good unless it's something AMAZING. Shadowing on the other hand, yes by all means go for it if you can land one. It's not meant to be a long commitment anyway, and you don't get much out of it by doing more than 20 hours on the same person.
4)Do my summer plans make sense? Is there anything else I should be doing?
Seems good to me! Id try to take it a bit easy.. you are going to have to work your butt off in the SMP for the whole year, so I wouldn't go in to it burnt out.
5) Should I ask for recs from my current teachers, or just wait until the masters program?
I would recommend using a quiver service such as interfolio. You never know what's going to happen. Ask your professors to tweak your SMP letter a bit to make it a med school rec (shouldn't be too hard since they should be similiar anyway). Then, you can pick and choose which to send after you have taken your SMP classes and evalulate the potential strength of letters that your SMP professors can provide. Much better than going back on your current professors down the road when they don't remember you as well.
6)When applying to the masters programs, should I mention my illnesses and injury, which I believe I have moved past, or should I just focus on positive things?
Who says your mental illness can't be a positive thing? If it helped you learn and become a stronger, more disciplined person by overcoming it, then you can certainly turn that into an asset.
7) Does my timeline sound right? Is there anything else you suggest?
I think your plans are pretty solid! Don't be so hard on yourself 🙂 I hope this helped. Best of luck to you