Starting over six years again after Ph.D.
First of all, you don't need a job at most colleges, you just need one of them. So don't let a bunch of closed doors bother you. Many others are still open.

You can definitely still do postdocs. Some schools have strict rules, many others do not, treating it as a generic at-will employment job with whatever name the prof wants to give the role. I knew someone who came back to a postdoc after over a decade in industry (they left again in a few months for another industry job though). I know others who have stayed in the role for way too many years. There are also similar jobs with other names like research scientist that you can get in academic labs. It's kind of wide open if you are willing/able to relocate. Pick some big schools and monitor their job opening list. 

You can also take classes at many (perhaps all?) major public universities via some variant of an open university system, requiring little more than permission of the instructor (and some cash). There will likely be a limit in the number of classes you can take this way but it can get you started. Ace a few classes and you will have a much easier time moving to the next step. 

Lack of ABET certification is not a huge deal, by the way. It's a lot of paperwork and many universities don't bother with it. It's more important that the school is regionally accredited. Then we can trust (at least somewhat more) that you were actually taught what your transcript says you were taught.