Mitch, The steel cap your refuring to is called the "Lash cap". Its supposed to be used on the exhaust valve and one of the valve spring retainers should have a area where the OD of the valve lash cap will sit in. So its possable you have the wrong retainer on the wrong valve. Hope that helps. And the plug wire coming off a tiny bit is no big deal. The coil wire on my dragster feels loose but its no probelem so far. But remember spark plug wire isnt actually a wire like coppor or steel, It is a speicel braided conductor so dont try to solder or crimp it.
Tyler.