I'll add 2 more cents. If this has not gone to collections yet I wouldn't wait too long with a PFD attempt. A collection will be a new, additional major negative in your file and will tank your scores even more. Paying off this CO won't remove the CO itself but it will lower your utilization and that will help your score
You just don't know how much time you have before this is sent to collections (if ever) but I personally would not take a chance of that happening.
Whatever you decide to do keep us all informed about your progress.
From a BK years ago to:
EX - 3/11 pulled by lender- 835, EQ - 2/11-816, TU - 2/11-782
"Some people spend an entire lifetime wondering if they've made a difference. The Marines don't have that problem".