That doesn’t make a lot of sense.
I’ve personally given slack to REL on the the issue of treachery against the US because I recognize that he was caught in a dilemma - honor his oath to defend the United States Constitution even though it meant that he could be opposing his immediate friends and family (while paradoxically defending people who were openly hostile to him) or throw in with the locals - and walk away from his oath.
Admittedly hard choices, he chose to reject the Constitution.
No he didn't. The Constitution does not forbid secession. If anything, it specifically allows it based on the fact that nobody called for the rejection of the ratification by New York, Virginia and Rhode Island.
In 1789, everyone knew what they meant when they wrote the US Constitution, and if no one objecting to New York, Virginia and Rhode Island's statements, it's because they were accepted as valid.