There's still quite a few weeks before the half term, so there will be other chances to interview- I don't think you should give up.
Also, this is probably the hardest time of the year to find a new job, I think, as everyone is interviewing and keen to move. If you're brave enough to take the leap to hand in your notice without a job, it will be much easier to secure a job after May half term, as there will be so much less competition.
I'd also add, if you really want to get out, prioritise applying for jobs and interviews over your current job. I know it's very hard, but if you do your applications/interview lessons, you'll be tired and rush through it. Instead, prioritise them, and rush your planning for your current class. I know that sounds brutal, though!
You've had some really good advice on interview answers.
I'd say try to find examples for all the common things you could be asked about e.g. behaviour management, progress, planning, literacy, strengths and weaknesses, curriculum and so on.
Also, at interview, really try and show what you can add to the school- e.g. extra curricular, experience in a specific subject area. Even if they don't specifically mention it, sometimes things like being willing and able to run e.g. a school music group or similar can sway things between two similar candidates. The school might not even know they want X club, or X sports team, but suddenly you mention it, and it may be the deciding factor.