Noisy X-axis maintenance advice  

Noisy X-axis maintenance advice

I've been the (mostly) happy owner of a MK3 since May, but my printer has been slowly developing a worsening case of what seems to be a fairly common issue with the X-axis; where the belt twists &/or always sits on one side of the X-axis idler (due to the top & bottom not running parallel?), causing squeaking/grinding/clicking noises & rubbing of the belt (evidenced by a build-up of black rubber dust in the X-axis idler assembly).

You can see the twisting of the belt in this video -

And how the top & bottom don't run parallel in this video -

I've found a lot of threads discussing this issue, with a lot of possible solutions. However I was hoping that somebody with experience of the issue could summarise/give me the 'best practice' approach to dealing with it. From looking through all of the existing threads, I've come across a whole bunch of different things that purportedly might fix my problem, but a more definitive answer (if there is one!) would be much appreciated.

While my printer still seems to print fine, the noise is now sometimes so bad (like fingernails on a blackboard) that I'm now resigned to dismantling it for a thorough service. Before I do, I have a few specific questions in addition to any general advice about addressing the issue -

1.) I have already printed a new R3 X-axis idler assembly in PET-G, in case when I dismantle the printer I discover that the current R3 part is worn & needs replacing. While I still have the printer assembled, is it worth printing something like this modified version of the X-axis idler assembly that claims to address the issue? I'm suspicious about the lack of comments, has anybody tried this? https://www.thingiverse.com/thing:2939488

2.) While I still have the printer assembled, would it be worth printing a new X-axis carriage back plate with belt access? This doesn't need to be black, right? https://www.thingiverse.com/thing:2727523

3.) When I have the printer dismantled, it would seem a pity not to upgrade the extruder parts to the new R3 B7 parts, however I don't have any black PET-G or ABS. Is there a known good source in the UK/EU to buy these parts printed, or a community favourite 3DHubs outfit?

4.) Where can I buy a replacement X-axis idler bearing/pulley? I am half expecting to find the bearings in the current one to be bad when I disassemble.

And lastly just to answer some basic questions that may get posed -

Yes, my X-axis motor pulley is mounted the correct way on the motor shaft (teeth toward the motor body).

Yes, my X-axis tension is within the recommended range.