Welcome to the forums!
I'd suggest reading the following:
Common Abbreviations
Credit Scoring 101 - great for knowing what is in your credit score and to see how your score is impacted.
What Steps Do I Take - great for learning the repair process.
and Example letters - PFDs, GWs, DVs, etc.
SM - I'll let others post on that one per rehabbing and so forth, but if you are current now, send GW letters.
CB of Det - Send a DV. If they verify for each and you agree with the debt, then send one PFD for the total amount (or settle). If they agree in writing that they'll delete in exchange for a payment, then pay it and they'll delete.
IC Systems - DV then send a PFD if you agree to the debt.
Verizon - send a PFD. If you might disagree with the debt, then certainly call them and ask for statements, etc.
2008 SL - send a GW.
DT Credit Co - If this is the lender, send a PFD. If a CA, then send a DV followed by a PFD. Or wait it out. They can report for 7 to 7.5 years from the DOFD of the debt (when you first went late and never recovered). They are allowed to report monthly if they wanted to, but they can't report longer than those 7-7.5 yrs from DOFD (11/05 I'm guessing). Your CRs will have the est. drop off date for TU and EX, and DOFD for EQ.
United#1 - DV then PFD.
United#2 - You've aready been sued. If the collection reports only, send a PFD. If both a judgment and collection report, then know that some have had success in removing judgments by paying it and asking the plaintiff's attorney to ask the court to have it vacated and that often leads to a removal. You can always ask them to delete the collection at the same time.
RJM - they are easy to deal with. Send a PFD.
Natlcrsys - DV then PFD.
NCO - DV then PFD.
LDC - DV then PFD.
Medical - DV then PFD.
Judgment - again the same as the one above....pay it and ask the plaintiff's attorney if they can ask the court to vacate.
Disclaimer: Keep an eye on your SOL. Unless your statute of limitations for your state has expired, do not send any letters, make any calls, or do anything unless you have the $$$ set aside to pay in full if you had to. You can always settle in the future if you wanted to, but many OCs/CAs are sue happy and doing anything inside of SOL can get you sued. If SOL didn't expire or if you didn't have the $$$ to PIF if you had to, then wait it out.
Judging by the dates, in all likelihood, some of what you posted is beyond your state's SOL. In other words, you are safe for some. Filing a BK would only make things worse and some of these folks can't come after you anyway. Plus it won't make all of the accounts go away because it happened pre-BK and they'll set you back years from buying a home. I think with some effort and time, you can get rid of half of your list within 3 months. I bet you can get rid of all of it within a year. After you get rid of most, then aim for a secured card from somewhere and it'll be easier to obtain.