Glad FO took action
I have heard that with some airlines / cultures there is a very strong reluctance among flight deck second-in-commands to question, correct, or overrule the first-in-command even if safety is being compromised. I'm glad this first officer took the action that he did.
One part of this story that intrigues me is the first officer arranging for an off duty pilot to join him on the flight deck for the balance of the flight. Is it common practice for the crew up front to be informed of other flight deck crew on board and where they are seated? This seems like a good policy - an extension of prudent resource management in a way.
As for the pilot's treatment through the US medical and justice system, the fact that he was in a hospital for several days prior to his first court appearance suggests to me that an evaluation was made regarding his motivations and his longer term mental state. I sure hope that where ever he is detained or allowed to reside in the short term he continues to receive the best possible medical care. At risk of revealing my bias, I do wonder if he would have been treated differently had his airplane landed in California rather than Texas.