1) It's usually worth trying to resolve negatives. How much trying depends on how much energy you care to put into it. With no energy, it'll fall off eventually. While you can theoretically be sued, if your credit is fairly thrashed and they don't think you have resources and it's not a lot of $, generally you won't be. The threshhold differs for each company, though.
2) Settling or paying negatives in full may hurt your score. Those amounts are in the range where you probably will be sued on one or the other, and a judgment will hurt more and for longer than trying to settle will.
3) I started 100 points lower than you, so there is hope. If those are credit cards that are charged off, you probably won't get a score increase from paying down your current cards, because you're utilization is still over 100% either way (because of the charged-off cards being overlimit).
4) It can remain on your report seven years from the date of first delinquency, so sometime in 2008.