This link may answer your questions: https://www.ssa.gov/benefits/retirement/planner/applying7.html#h4

Go to the website of your county courthouse and do a case search by name. Then you'll know if there has been a lawsuit filed against you.

I suggest that you have a conversation with a local real estate attorney and discuss the sale and partition of the property.

Paying debts for someone on SSI is the same as giving them money and will reduce your benefits on a dollar for dollar basis. I advise caution.

A $745 dispute can be brought in small claims court. A lawyer would not get involved in such a dispute.

You have no freedom of speech rights from a private company.

And? Were you injured in some way? Did you require significant medical attention? If not, you have no damages to support any legal action.

POA can only be granted voluntarily by someone with the capacity to do so. If your uncle is incapable of granting POA then perhaps you should...

As a general rule, a business is not responsible for the criminal acts of others.

Absent injuries requiring significant medical care you would not have sufficient damages to warrant legal action in my opinion.