Saying prayers for good things to happen in your life, Zoe. I can't help but feel that if you do get fired by these folks, it will turn out to be a blessing in disguise, as you are not happy in that job and they do not treat you well and nothing you do seems to make it better. I think you deserve to be much happier at work and a better job is definitely out there for you!
If you don't get fired, but they have some "plan for improvement" this is a great warning to keep going with your plan to seek a new job. I would go so far as saying that the universe may want you to be teaching somewhere else, in another state. Florida is very aggressively looking for teachers, and you do not have a mortgage or even a lease in two months, and you could sub down there, too. It might be a fun thing to do for a few years--you can always live lightly and go back to Colorado after a break.
And buy a cheap computer if you cannot do your job searching with what you have. Walmart tends to have the best cheap computer prices.
You are a valuable person, and skilled, creative, and competent. Do not let these folks make you feel bad about yourself anymore.