Dear Rosie:
You wrote that the job is “very physical”. Does it mean that it helps you keep in good physical shape? That may be an advantage, a benefit if you need that practice. (If it is possible that you may get physically injured doing the job, that needs to be another consideration).
It pays well, you hate it, it feels like a nightmare, you asked for a vacation and was denied, you are looking for another job and you don’t want to leave this job before you have another. You are doing all that is possible unless you move to another area of the country or the world where the job market in your field is significantly better, if such a place exists. If moving in not an option, the only suggestion I have for you, one I practiced myself, is to learn the skill of enduring suffering.
Sort of relaxing into it, taking a deep breath and accepting how badly it feels. No longer yearning for a way out, but accepting what you feel and that you will continue to feel this way for a while.
There is great benefit in developing this (odd sounding, perhaps) skill, of not only surviving this kind of suffering, but enduring it with peace, with equanimity, continuing to function well even though you hate it. It will be useful because there is plenty more of this to come, in any job, in any relationship, and as a parent, if you choose to be one.
There is confidence and well being gained with this practice, knowing that you can endure, that you can function well no matter how you feel.
anita