I would guess that if you filled out the FAFSA, you would qualify for a fair amount of educational financial aid. You could enroll in a community college without the SAT. Most will start you with remediation courses in subject areas you are deficient in and then move you into regular coursework. Many community colleges have programs in software/app development which (if I remember from another post) is something you might be interested in. Once you have taken a year or two of successful coursework at a community college, you can generally get transferred into a university based on your proven community college grades and the SAT never even comes into play.

Another option is that many public school districts offer adult education classes. That might be another way to remediate your math skills under a bit more structure and with more academic support -- again, generally very affordable.

As far as nutrition goes, most communities have food banks/charities that may be able to help you obtain healthier food.

Even if you have no experience, you might be able to find a job that will certainly bring in more than $300/month and allow you to eat a bit healthier without putting your health at risk through constant plasma donation.