They are in recess, but did not officially call it that so much that needs to be acted upon is in limbo. It was likely done on purpose to keep the President’s hands tied.
He just told them to get back to work, or else.
That is correct. All he has to do is say, you need to get back into session by such and such a time or else.
They dont, and he can adjourn them till next Jan when they convene to swear in a new congress.