So I swapped the worn stock arm on my extruder with another of the same design (which fixed the looseness of the non-driven gear), but that did not fix the underextrusion. I also replaced the bowden tube and coupler which helped a bit. And now I have swapped the nozzle with this one from Amazon, and from the looks of it, it is a pretty nice looking nozzle, however the first print was not perfect (had some boogers) - but I am still testing it. I am hopeful that this new nozzle will work for my printer, since it looks very well made (almost appears polished inside which is not found on cheap packs of MK8 nozzles typically). I have some longer prints lined up which should be a better test.
My mission is to lower the collective IQ of teh Internets one post at a time.