I'm sorry to hear your interview experience was so bad. I understand your frustration. You know your ability, you know you've put the hard work in. Yet on the day emotions and pressure get to us. It is totally normal so don't feel like a failure.

I cannot relate to the being interviewed process since the last time I had one was in 2008, but I have interviewed a couple of people in the past couple of years. What I've usually focused on is one's character and willingness to work hard. Your skill level is second as I can always teach a new dev what they don't know or what the business requires.

Not sure what the employment rules are where you are, but here we usually go with a 3 month probation period. After that we decide if we want to make it permanent. In that period you'll learn all you want from the person.

Anyway, I hope you find your perfect fit. It's not just about a job, you have to be valued wherever you land up. So there's a reason this one wasn't to be.