My advice if you are looking to study, is to try and build on the skills you have.
Without industry experience in the field you choose to study in, for most degrees it will be a few years AFTER you finish study before you are back to where you are now income wise.
Have you considered something like a management course, some of which can be done in addition to your current job, so you don't have to make a financial sacrifice to get something out of it?
Just thinking out loud here for you.