and yes the fat Octave roll (between 1.79mm and 2.01mm had lots of chewing. thats why I need to get a brush in to it to get teeth cleaned out. was just wondering how hard that spring will be to compress when reassembling tensioner. I already blew out all I can but even idler wheel has dust packed on it and cant clean all that whith it assembled. and can I oil the idler bearing?

I did it and oiled bearing then dabbed with tissue any excess oil and bearing will spin a couple times when flicked now. reassembled and ready to test printing. not much stuck in geared teeth just a couple hard specks on roller which may have let it slip sometimes.

Before you have a full blown nightmare, print a new extruder. The MK5 is proven to work with the stock PEEK hotend and makes maintenance much easier. I know you have been having issues with your machine, and if you put this off, you may eventually break the acrylic and napalm your printer. Better to have it and not need it.
Also, When switching between filaments, if one is significantly larger than the other (0.1+/-) you want to adjust your tension arm. If your extruder is expecting a smaller diameter, too much material will be forced down and eventually jam. You can make all the software adjustments you want, but the spring is just a spring and cannot be commanded on what to expect. Too much tension will cause the drive gear to chew through the line....I think this may be the cause of your current dilemma.