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Paying off the CO will help revolving utilization and get the line drawn in the sand there.
Getting current on the 90D late you should do as well as but that won't improve your score much unless it makes a meaningful difference to your revolving utilization.
The collections: post them over in Rebuilding and see if you can get them off your reports altogether via a pay for delete (PFD) or other technique as paying them won't help at all, but if you can get them off it's a huge win credit wise especially if those are your only public records (collections basically count similarly as tax liens and judgements) on your report.
Not familiar with Carrington but I haven't been paying much attention to the mortgage market (or forums, my bad) as of late; I think you need to get to around 580 for FHA still though, which is a big maybe... but right now just stop the bleeding is the first step.