I have been on the other side of the hiring table and I have to say that just flat out... it is hard to pick. Most of the time all the candidates have something promising to give. And for me personally the interview doesn't mean much unless you completely blow it, which usually means something like you were a poor speaker for a job that requires a good speaker.

If you don't want to be fired at will you should look into government work. Even if you aren't part of a union most of the time gov'ts culture is to try to keep people if they can.

At one point in my career I thought I was getting fired. I saw in the minutes of the manager meeting that they were preparing an advertisement for my job (I wasn't supposed to have access to it). I called the boss and told him I wanted to know what was happening... (without mentioning what I saw) to my shock he was very supportive and told me he valued me and would help me get the position. He did. I was amazed. So I do feel that if you are a good worker gov't does see its role as helping to keep people employed if they can.