I know subbing can be unpleasant work (I've done it, and I definitely remember terrible pay and feeling like a non-entity at school), but remember that there can be great opportunities in it too. I went out of my way to be really nice and friendly to other teachers, eventually got a long-term subbing position in a special needs classroom, and got a great letter of reference out of it from the teacher in charge of the classroom. I know other teachers who have been able to turn long-term sub positions into permanent teaching positions.
Just recently, a substitute teacher in my school emailed me asking if he could come observe a few of my classes. He's young and eager to become a full time teacher, he's been subbing this fall in the interest of pursuing that goal, and he's interested in teaching in my subject area. He got permission from our sub coordinator to observe other classes during his free periods, asked my department head if he could contact people in my department, and sent me an email asking if he could visit my classes. He subbed for me last month and did a wonderful job (the kids kept telling me how helpful he was and how much they got done, which is the highest praise a substitute can get in my book), so I was happy to say yes. I haven't met this guy yet, but I'm impressed already because he's being very smart here. If I have a planned absence, I'll ask for him based on my students' positive experience with him (increasing his money-making opportunities) and he's also trying to build positive relationships at the school, which can only help him in applying for a job, at my school or another - you never know what connection can help you out with that.
I know subbing is frustrating work (I can imagine that years of it would be enough to get anyone down), but I just thought I'd throw my two cents in - remember that there can also be opportunities in it. Like anything else, you usually get out what you put in. With that being said though, best of luck with the job search! Teaching is MUCH better when you have your own classroom and a full time, permanent position. I wouldn't want to go back to subbing either, and I imagine years of it would be enough to try the patience of a saint.