Spark Plug: It could be a number of things but I'm thinking that the rings aren't broken in yet so you're getting a little blow by. The motor is still new, and I had a similar problem with cylinder #2 in my engine when I first got it going. The rings just didn't want to seat and I was thinking I was going to have to rebuild it again, but it eventually sealed after running it around town a bit. As for the oil on the outside, you may just have a small valve cover gasket leak. Also, depending on how loose the plug is, it's possible that oil could have been sucked in from the pool outside the head.
Exhaust smell in radiator fluid: It depends on how loose the head bolts are, but maybe your head gasket isn't getting a good seal. Torque them to spec and run it, and while you are, keep the cap off the radiator and look for bubbles when the thermostat opens. Granted it's a new motor, so you may still have some air in your cooling system, but a constant stream of bubble coming up is a sign of a bad head gasket.
Water on valvetrain: Is there any water anywhere else or just on that rocker? How about around the base of the springs? If you were spewing water oil there for some reason it wouldn't be isolated to that single spot.
Loose pushrod: I heard something move but wasn't sure if it was the pushrod or rocker I was hearing. Being able to twist the pushrod around is normal, but up and down movement is not. Did you reuese your stock pushrods or the ones that came with the used cam/lifters? You may just need to determine the correct length pushrod and order a set.
