Yes it's a dilly of a pickle. The 853 stays are probably the same thickness as 631 ones anyway, just unnecessarily strong and difficult to manipulate. You'd think that if it was really OK to heat them up like that Reynolds would say so. I don't think he should have used them but got you some cromoly or 631 stays and maybe a drive side yoke would be the best way to get the tyre and chainring clearance, or the S-bend Columbus stays might do it. I guess you could try going back and saying your tyres don't fit and you're not happy with him ignoring Reynolds advice on the tubes. If he replaces them again I don't think there will be any issue with the BB shell getting another heat cycle as they are very thick. Ditto the dropouts.