Well after a thorough refresh, my troublesome rye starter still had those acetone fumes but I tasted it and it wasn't at all unpleasant so I thought I may as well try and make a loaf from it before I ditched it. I did also use this starter to seed another spelt starter which now smells very different to it's original....in a good way! With a baby, husband and pets that all need entertaining on the weekend I didn't have time to follow the form/re-form technique during first proof and I also had trouble with the dough sticking to the cloth but I'll accept this as a first attempt. The flavour is distinctly sour and nutty - not at all bad so I think I'll persist with this rye starter while continuing to maintain the new spelt one also.
I think sometimes we can get a bit too cautious. I do recall doing something similar a while back with a newish starter and like you, the bread turned out just fine and nobody died. If there is acetone present, as I recall, it is pretty volatile and would be well and truly driven off during baking. However, the old adage 'better safe than sorry' does come to mind as well.
Also, there is nothing particularly sacrosanct about how long you have had your starter despite the fetish that some have about this fifty/hundred year old or whatever. I have heard that the tradition of unleavened bread during lent was more to do with renewing the leaven on an annual basis than with divine dictate.
Good luck with your projects.
I just found a blog post that says the acetone smell is attributed to ethyl acetate which is harmless. I wonder if anyone would care to comment before I share this loaf around??