I’ve done a lot of low rate or entirely volunteer work for small, often non-profit organizations in the past, and don’t fall into the trap. It can be thankless and it can be soul sucking.
However, obviously if you want to eat and if this is your only income right now you’ll have to stick it out a bit. So I hope we are talking like you are virtually working no hours for that rate, leaving you time to expand your resume on your own.
I have often been asked in the past by friends or acquaintances how you get a good career in programming, and the answer typically is either luck, or a lot of your own hard work.
I don’t know what the job market is like these days, but historically your papers mean very little to getting a job. A link to your Github goes a long way to demonstrate your abilities and provides a much higher degree of confidence you know what you are doing because they can actually look at your work, and if you are contributing to other projects, that you are a team player. As one speaker said at a Google Q&A I watched when asked if a PhD would increase their chance of getting hired: “well, we won’t hold having a PhD against you”.
There is also a lot of free course material out there to various degrees of difficulty.
Programming is becoming more and more competitive, and the ones that succeed have made it their passion, which does mean a lot of unpaid work. So either find projects you are happy to provide your time to to sharpen your skill, or start your own project that you can get satisfaction in building. Actually programming something is always the fastest way to improve your skill.
No idea on the current market myself. You should absolutely start looking at the rate you are being paid right now though. Just don’t get discouraged about the resume gap, it’s a rare field where you can make your own backfill for those gaps.