I have never sailed a Catalina 22, so I have no direct information to impart. But to answer a few questions...
1) this is the North sails tuning guide for your boat. http://www.onedesign.com/Portals/106/docs/Tuning Guides/north-catalina22-tuningguide.pdf
it is a really good place to start.
2)The reasons it doesn't matter if the leeward shrouds are loose is that they really aren't. Starting with the mast in column at the dock, and the shrouds snug. When you put up the sails the shrouds don't change leingth, but the leeward shrouds start to loosen. This is because the mast has fallen off to leeward and is no longer where it should be. The problem isn't that the leeward shrouds are to long, but that the windward shrouds are. So you need to tighten the windward shrouds until the mast is back in column.
The easiest way to do this is to tack the boat and tighten up the now leeward shrouds a bit then tack back over and see what happened. This gets a little confusing, and is why many people seem to think you tighten the leeward shrouds. Technically you do (since they are the leeward shrouds during the brief moments you are adjusting them), but you decide how much to tighten them while they are the windward ones.
3) the reason it doesn't matter how loose the leeward shrouds are is that... Well they really don't do anything. It is quite possible to take the leeward shrouds off the boat (not a good idea however). And for some extreme boats it has actually been contemplated while doing things like the transpac where you are on starboard tack for weeks at a time to reduce windage.
It is never a good idea to have things just bouncing around, but in reality if the shrouds are properly tightened for the conditions the leeward shrouds shouldn't be much looser than they were at the dock since the mast is in the same place. Excluding times in very light air where you don't need any pressure on some shrouds (J-22 in <3kn of breeze for instance).
4) the rig won't slam over, what happens is as the mast moves back to centerline the shrouds equalize pressure and transfer the load. If the mast doesn't move relative to the boat then there is no slamming. If it does then the windward shrouds were too loose, not the leeward ones.