Luis,
On your 18", always spin the lock to the right, everytime you open or close the door, thereby always tightening the mechanism. You sure went from stick burning to Weber cooking fast! Love it!
I have a little gap on my 22, but don't want to deal with bending it. My 18 has a nice coating, so no leaks there. The only time the gap is an issue is when I shut down the cooker, but now I throw the lid from a performer on top to shut it down. Might get an SS from Cajun Bandit one day just because I like the look... or I could spend the money on meat.