Phew, that will be a relief - a high note on which to end the week - onwards and upwards!
Just a point about placing another (working) radio close to the MR10 to check if the oscillator is running or not by listening for the non-working set's heterodyne on the working radio, doesn't the second radio need to be on the same IF frequency? The IF frequency of the MR10 is a bit odd, in that it's 422 kHz, whereas most UK post-war radios tend to be 465kHz (EG Bush DAC90A) or 470kHz (EG Bush TR82).
Now that the MR10 is working again on AM as well as FM, if only out of curiosity and a learning experience (for me, at any rate!), it might be worth tuning the MR10 across the AM bands to see if - despite the second radio placed next to the MR10 having a 465/470 kHz IF - nevertheless, a heterodyne is heard on the second radio.
As to 'not getting anywhere with the Nostalgair tests and your signal tracer', in fact you were, because the tests showed that the oscillator wasn't working, just as if - for example - you put an Ohmmeter across a fuse and 'get no reading', it proves that the fuse has blown.