Any question answered...

I'm not a podiatrist or expert in any related capacity.

Maybe consider the bike whisperer for a cleat fitting?

I would suggest you try and adjust the cleat alignment, possibly a foot bed will help.

Even better ignore all the online diagnoses and see a professional

I suspect the main reason my road bike feels so good is that it has been fitted by Scherrit!

Thanks for the advice, I'll have a play and see how I get on.