What is the safest way for a partially disabled person in the USA to use prison for food and shelter as an alternative to dying homeless in a gutter on a cold rainy night?

You probably want to go to a minimum security federal prison. The easiest way to get there that I think of is check fraud.

You'll need to write a bunch or bad checks in as many states as you can, or send them through the mail. You'll need to do this a lot, and for a pretty significant amount of money otherwise they'll just give you probation of some sort.

Having a disability might be a problem though; if it costs too much medically to keep you in prison they'll just out you back on the street as a compassionate release.