@cullenb Whoo, this takes me back. I had a time of figuring these out on of my my XPs awhile ago.
I found that if I put a trigger on the text box that when the Enter key was pressed, that it closed the keyboard/exited editing mode.
As far as the X staying up on the keyboard, I just made sure that the “Allow Close” property was checked on the XP-wide keyboard settings. If the keyboard is up and the user is typing, it tends to stay up. The X disappears when the user presses somewhere else while in text editing mode, but if they touch the keyboard again, it should come back up. Let me know if this helps!