1. The long tiller extension is more of a technique thing. Sit all the way forward so that your forward leg is right up against the front of the cockpit. There is a tendency to slide aft. Hold the tiller extension across your body and not like a frying pan aft of your body. As you tack, you push the extension away from you and follow it across the boat, it doesn't take long to get used to the longer extension. If after a while you still don't like it, cut 6" off. Check out videos of tacking a Laser on Youtube, there are lots.
2. There should be a small hold on the top of the rudder head and a similar hole in the end of the tiller where you can put a pin. The pin should be tied to the rudder head so you won't lose it. You don't actually need to use the pin. Pass the rudder downhaul line through the cleat (there's often a 2:1 system so you can pull tighter) and then do a couple of hitches around the tiller on the forward side of the cleat. That will prevent it from creeping out.
3. That's a unique system for the outhaul but I'm sure it's perfectly legal. Soft attachment methods are used a lot these days. Most Lasers use a shackle attached to a block or a hook attached to a block(my choice) to allow for an easy moving 2:1 at the end of the boom.
4. Yes, normal wet sanding but be gentle as the foam blades have a thin coat of white.
5. It sounds like the shock cord needs to be a little bit tighter so just snug it up or maybe the shock cord needs replacing if it's old. It's standard stuff for it to pop up a little. Often times on a tack just take a glance at your daggerboard and make sure it's down, if not, give it a little push. It's a symptom of the design but not a big deal. Usually once underway upwind it stays in the full down position.