Your career history looks scarily like my brother’s!
If you have been totally out of work for 3 years then you obviously need to change tact. And probably change your CV. If you aren’t getting interviews and they say it’s because you are ‘over qualified’ then you probably writing it like a post-doc application. In which case completely rearrange it to be skills-with-examples (matched to each application you make), then education as a simple list.
I would highly encourage you to look at all pay grades, even if it feels like starting afresh. If asked, explain that your post doc experience wasn’t what you hoped for and you want to change fields. Depending what type of chemistry you did, as well as the standard chemistry, oil&gas industries, teaching or HSE, some additional options could be: scientific coding / software development or sales; lab work, including biosciences, materials science; proof-reading / publishing; or quality control and testing. Cambridge has a vast bio-medical sector for example. It is better to have a low paid job than no job at all, IMO. Every so often more ‘interesting’ analytical chemistry jobs come up in the environmental sector, for example in ice cores for British Antarctic Survey.