Hi Daniel,
First off I'd like to welcome you the the GTA,,,, it's nice to have you with us :)
As for the Storm XT,,, I don't own one so I don't have any first hand experience with that rifle, but I'm sure there are plenty of GTA members who are familiar and who will chime in as far as mods for the gun. I am pretty sure that Bobs (Charliedatuna) GRTIII trigger blade will fit in the rifle and if I'm right then that would be the first "mod" I would take care of. That trigger will be the best money you ever spend on your rifle. Like I said,,, I'm pretty sure it fits in your rifle but the other members can verify that.
AS for the scope creep,,,,, you didn't say what kind of scope mount you have on the gun. I'll assume it's the one that came with the gun, but whatever kind it is it's apparently not getting the job done. Do yourself a favor and get an "Accushot" one piece mount, it costs like $16 bucks from Pyramydair.com or several other places. Install the accushot 1 piece and your scope problems will be a thing of the past. Just remember to clean EVERYTHING with denatured alcohol before installation. Clean every part of the mount,,, screws included, and also clean the top of the rifle receiver and the inside of the grooved dovetails. Make sure there isn't even the slightest hint of grease or oil anywhere. Then install the mount and scope and use a drop of blue loc-tite on the screws and a dab on the dovetail grooves. Your scope will stay put forever if done correctly.
As for pellets,,,,, for hunting my primary hunting pellet is the JSB Predator pellet,,,, but I am also fond of Crosman Premier Light domed pellets ... (CPL's). Best thing to do is get a variety of pellets and do some grouping tests with your gun. See which pellets group the best at your average hunting range then pick a pellet from them.
As for what you can hunt,,,,,, the other membes will have to chime in as I've never been to California so I'm of no use there.
Again,,, welcome,,, looking forward to your future posts.....
Jeff