Changing fields in postdoc. Whether or not to pursue another postdoc at 35
Ask yourself what the trade-off is. There are basically three possible outcomes: (i) You quit now and do something else. (ii) You take the postdoc but don't get a faculty position after that, so do something else. (iii) You take the postdoc and do get a faculty position after that.

The way you describe it, you love doing what you do. So options (ii) and (iii) involve doing something you really enjoy, with the possibility of being able to do that for your entire life. In the worst case, you only get to do it for a few more years.

Options (i) and (ii) involve having to find a different job. The only reason why (ii) would seem to be a bad choice would be if you think that the job you can get after another postdoc is worse than what you could get now. But I don't really see why that would be so. So the long-term prospects for (ii) are no worse than for (i), but (ii) involves doing something you enjoy.