Well, finally managed to get some definitive answers from Dr today after the seemingly endless batteries of tests over the last year. The bad news is there is nothing that can really be done about my condition and in the long term it will be the end of me if I live that long. The good news is in the short term i am in no immediate danger and the more high intensity exercise I do, the better. So that's good.
I celebrated with an intense chest and arms workout, although suffered a classic brain fog in the middle of it: I was meant to increase my weight in the overhead push, just by 2.5kg, but was horrified to find I could barely lift the bar. I almost dropped it after 3 reps let alone 3 sets of 8-12. So I dropped back to the previous weight and was again horrified to find that was almost impossible to lift above my head too.
We all have bad days so I just chalked it up to that and went on with the next exercise.
It was only when I was stripping the plates off at the end that I discovered I had counted a pair of 15s as 5s, so was already 20kg over my start point.
Maybe I should just stick to the running.