Tap the brass tube back in the petcock. You are done. Don't do all that other stuff. A simple tap is all it needs. You don't need another petcock. OK, let me state another way. If the tube can be tapped back in place and you can't pull it out by hand (use no tools, but your fingers) as hard as you can pull on it, then no......you don't need to replace the petcock.
JFYI, I have never replaced a petcock because the tube didn't stay in place. This is talking about being in the field for many years (working on a lot of bikes)....not my personal equipment.