Bad verticals and strings. Ideas?

Hi folks,
I've made some progress, but I feel like I'm hitting a wall, so I'm hoping for some new advice.

As you can see in the pics, I have definite string issues, and the vertical walls look pretty bad. I've calibrated x, y, z, extrusuion; all come out good. I use a fan on the hotend, print with .2 mm layers, and very slow - 15 mm/s.
I'm printing on a RepRap Pursa 2, PLA @ 185C, heated bed @ 70C, onto Painter's tape.

What should I try next?

Thanks!

I know when I was having that issue I adjusted the extrusion multiplier and retraction, that seemed to resolve my issue. But each printer is different so I could be off.

Bob

Ok, that's somewhere to start.

I assume retraction is to fix the strings. It was set to 1, I'll try 2mm?

And extrusion multiplier to fix the verticals? Also, I'm using Slic3r and don't see a setting actually called "extrusion multiplier." I think Print Settings>Advanced>Default Extrusion Width is closest. Do I want it to be greater than my nozzle diameter? Less?

Thanks for the response!

I see a lot of missing perimeters. I suspect the extruder is slipping, on the verge of jamming. Maybe try a little higher temperature. Get it looking consistent, then calibrate the extruder again.

It in the Filament Settings tab in Slic3r