The first time I heard someone suggest LHO had picked up the revolver at his boardinghouse room, I didn't see any proof that this took place only that it was possible. You believe he was given the revolver at the theater, tell me what is it that makes you arrive at that conclusion versus when he started his day or just about any other time where this could be possible.
Here's a possible imaginary dialog the could have been recorded inside the Texas Theater on 11/22/63....
"Hi Lee...I'm sure glad to see you. There's been a change in the plan.... Our plan was to make it appear that you, and
Juan had tried to shoot JFK, but missed and then we were going escort you out of the country so you could seek asylum in Cuba, ... Well something's gone wrong..... it looks like someone has actually shot the President....But we don't know if that's true,.... yet. Stuff has hit the fan and we don't know what's going on at the moment, but you could be in danger. Here's your pistol and some ammo.... just in case..... Stay here in the Theater.... I'll be back later... After we learn more.....