Glad you're making progress. As for the bowden tube how about getting rid of it altogether? I can see the point of them but they are a workaround for the problem of trying to get the mass off the effector (or carriage). There are numerous inherent reasons why they are bad, the filament is a loose fit in the tube and basically has to be or it would bind (the problem you've been having), because of this the filament can spiral inside the tube under pressure, exhibiting elastic properties, and it might even have some elasticity f its own. All of this adds up to far less precise filament control.
Sure you can buy new fangled capricorn 1.8mm bowden tube with (and I struggle to believe this) even slipperier teflon, you can put cooking oil on your filament cleaning sponge, you can use pressure advance on RRF/Duet to offset the elastic effect caused by the bowden tube. These are all great bodges, but are blown entirely out of the water by two other approaches. The flying extruder, which shortens (by around 2/3), and straightens your bowden tube moving the extruder to a platform suspended on elastic above the effector, You can also achieve this like Deckingman has on a corexy with a passive or active second gantry for your extruder/s and the flexible drive extruder where a remote (and stationary) motor turns a flex-shaft to drive a direct extruder on the effector or carriage.
I wouldn't have been able to see the difference if when I had a kossel mini, I didn't also have an i3. The difference in precision of laying down filament directly rather than via the tube was very apparent.
If you are going to keep your bowden tube make it as short as possible, mount the extruder midway up a tower and eliminate as much bend as possible.
