...called the Sabbath. It is part of the 10 Commandments. This does not exist in other ANE law collections.

Shabbadu originated in Mesopotamian cultures as a day where it was considered not fortunate to do work.

fugitive slaves are not required to be returned to their masters ([Deuteronomy 23:16-17]), while for example,

There's no indication in those verses whether it regards to Hebrew or non-Hebrew slaves. Of course, Deuteronomy and Leviticus are inconsistent in many areas, you would expect slavery to be the same.

For what it's worth Onkelos translates it as a Jewish slave owned by a non-Jewish master. The Talmud (Gittin 45a) as referenced by Rashi says it also applies to a non-Jewish slave who fled into Israel from outside Israel. Neither say it applies to the case you would like it to.

As I pointed to above, Torah law is in stark contrast to ANE law when it comes to flagrant abuse by a slavemaster, where the Torah affords protection, while the other ANE law collections demonstrate a complete lack of this protection.

I would agree that the Torah (Iron Age) is a moral improvement over the Hammurabic Laws (Bronze Age) with regard to slavery. But that's not all that impressive. I also disagree that it's in "stark contrast." It's slightly better in some cases, and slightly worse in others, and in other cases it mimics the Babylonian laws almost to the letter.

The Torah's laws have many aspects that provide many more protections than other contemporary laws.

Really? I'll take this over the Torah's laws any time.

Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.