The US Supreme Court has ruled that when a person is unable to pay fines or restitution because he is too poor to be able to do so, the courts can try to find some alternative to incarceration for the defendant. In other words, it is not a crime to be poor, and despite what probation may recommend, the judge does not have to resentence you to jail for his failure to pay, if it is clear that you have made every good faith effort to do the best you can under your financial constraints. It is when a defendant is capable of affording restitution and ducking his obligation that he would have to worry about a violation and resentencing.
If you have been doing the very best you can, which is what it sounds like, you ought to be able to demonstrate that to the court. So if you get violated, at the end of your probation for your unpaid balance of restitution, you will have a hearing, where you can show that you made a good faith effort to pay as much as you was capable of. You could put together whatever official records you've got -- monthly bills, tax statements, and whatever else may be relevant to show just how hard you've consistently tried to do the right thing and with that counter Probation's violation.
The judge will generally decide to extend your probation so that you gets more time to pay, but it can instead enter your debt as a civil judgment so that your assets can be attached if you stop paying or your wages garnished. With a civil judgment, the criminal
court and probation will not monitor your compliance, and the judgment would be enforced like any other civil debt.
But you will be expected to pay restitution for as long as there is a balance outstanding, even after you are off of probation.