Five figures starts at 10,000 and ends at 99,999, so mid 5 figures is taken to mean around 50,000. But it is not strictly 50,000. For instance 45,000 or 55,000 are considered mid 5 figures as well.
'Schlepping' is not standard English. By that, I mean it is argot or maybe an adopted word used by only a narrow group of speakers/writers. I've never heard of it before and I am a native speaker ! I did a little research on it, and in this instance it means colloquially "dragging yourself" to work, or in more standard English going to work reluctantly because you have to.