Some do, some don't.
"Do they keep the Jewish Sabbath as a matter of religious law/theology?"
Some do, some don't.
"You can call me confused if you'd like, but you have to admit that the fact that Christians don't follow the Torah when the creator of their religion said to do so is, in fact, rather confusing."
No argument.
While that is strictly true, I think that it is more accurately a case of "some do, the vast majority do not." For instance, I think that the Seventh Day Adventists have a Saturday Sabbath, but Roman Catholics, Greek Orthodox, Russian Orthodox, Lutherans, Anglicans, and most of the other major (in terms of the number of adherents) Protestant churches have a Sunday Sabbath. This is similar to case of the laws of Kashrut (keeping kosher). As far as my experience goes, every Christian person that I've known has no religious restrictions on eating pork, mixing milk with meat, eating meat that was not slaughtered according to the very strict laws of Kashrut, and has no problem eating shellfish.
My own personal opinion is this (and it is just opinion, i.e. it may not be completely correct): Jesus saw a lot of corruption in the religious/Temple hierarchy and, being an idealist, was so morally outraged by what he saw that he began a movement to reform the system (i.e. really the people). [As an aside, by the time Jesus was born, the Romans had replaced the Temple and religious hierarchy, as well as the political hierarchy, with people naturally loyal to, or utterly dependent upon being loyal to, Rome - so the corruption was forced on Israel and the Jews]. After his death, Paul and later Church figures changed things quite a bit - they did change Judaism, so much so that they created a separate religion, one which (IMHO) Jesus himself wouldn't have recognized or tolerated. Later persecution of the Jews, especially after the revolt which resulted in the destruction of the Second Temple and the Bar Kochba rebellion circa 135 C.E., caused the leaders of the new religion to want to distance themselves even further from their mother religion, to avoid being caught up in the persecution and massacres. Again, all of this is my opinion, but it is based on lots of reading done over a couple of decades, including books on Jewish-Christian relations written by Christians, priests among them.
Thanks, BTW, for your open-mindedness and forthrightness. Others on this thread have, shall we say, not met your standards.