I'm so sorry your interview didn't go as well as you anticipated and that you're just fed up and done. I get that. I can go from highly positive to the depths of despair depending on situations too. Please let some of the emotional energy dissipate from the situation before you make major decisions.

You may be in a field of work that has limited opportunities so it would follow that it would take some time to find a job. Your job sounds highly specialized. Don't give up. Keep your eyes open to possibilities. I like someone's idea that you practice interviewing with someone. Take all of the questions that tripped you up and practice. There are also books on interview skills that are like gold for all the general questions. I always used them. You may impress them on the general questions so much that it blends over into the technical side.

I hope you feel better after you've slept on this. Are you safe tonight?

I believe in you and I think you have a wonderful future just around the corner out of view. Sending you big hugs and best wishes.