I have recent acquired a very nice Arrarex Caravel from Italy and have have pretty good success with my pulls...however I notice that there is always a very wet puck with water in the top of the portafilter when I take it off after a pull. Is there a leak somewhere?

I think that's just kind of how it works. You can do a bunch of short pulls after pulling the shot to dry out the puck if you want, but I don't even bother anymore.

Completely normal, you just need to pump the handle after your shot to drain all the remaining water out. I typically do this, then let it sit for about 30 seconds, and it's nice and dry.

Lift up just enough to feel the water drop under the seal, not enough to refill from the reservoir. I get enough water for almost a second shot, but if you taste it, not very tasty . I assume this is just to do with how the piston system was designed, not all the water is squeezed through the puck on the first pull.

Depends on how you pull.

For my single basket, I pull a single "Fellini"--about half way down--then finish with one full pull. Always a dry puck.