Welcome to OCDO! You have excellent questions and I am sure you will get many pertinent answers.
As for leaning on the gun, that comes with time and comfort levels. Many people tend to lean on it for various reasons. Mostly it's a subconcious way to know it's still there without placing your hand on it or being to obvious.
Strong side/weak side. Always best to keep your strong side away from people you are concerned about. This keeps your body between them and your firearm and helps prevent problems. Keeping in moid that a gun grab attempt would be a rare occurance.