Research Exercise: The Rights of Slaves

Recently I came across the following claim in a comments section following an article on blacks and the Confederacy.

Slaves had rights — very, very limited ones, to be sure, but rights nonetheless, some bestowed by law, some by custom. It varied by state, but their rights included support in sickness and old age when they could not work (forerunner to Medicare and Medicaid?); the right to lighter work for women, especially during pregnancy; the right to limited religious instruction; the right to marry; even the right to give testimony, in certain circumstances.

Well, folks, have at it.  How true are the claims made in the paragraph?

ADDITION: From the same source …

If you can’t document your claim with reliable source material from that era, becomes an anecdote and an opinion.

Note the source did not document her own claims in her comment.  Nor do I see documentation for this claim:

About 25% of the slave population was literate because their work required them to read and write (slave foremen of plantations had to be able to read state agricultural directives and complete reports on crop yield, etc.; slave builders had to be able to read blueprints, and so forth).