Lieberman is definitely shomer Shabat. I saw him a few weeks ago davening at an Orthodox synagogue erev Shabat.
Cantor may belong to an Orthodox synagogue, but he is not shomer Shabat. Or at least he was not last summer as he appeared at a public event on Shabat.
I don’t know about Gilman. What synagogue did he belong to?
There are other members of congress who have belonged to Orthodox synagogues. I am aware of Ben Cardin, Arlen Specter, and the late James Scheuer. There are probably others.