I'm not sure how you're testing but it's not possible for any metal part of the bike to be hot, they are all grounded and you should have fried a battery cable by now, unless there are other issues. I suspect you have a bad ground from the battery to the frame. you have also damaged the starter relay and it needs to be repaired. to do this, remove the negative battery cable at the battery. remove the positive battery cable at the starter/solenoid, unplug the other wire at the solenoid. drain the primary/trans lube. lossen the clutch cable to full slack and remove the primary cover. loosen the starter jackshaft bolt (hold the pinion gear with a pair of channel locks) and remove the starter. you can purchase a rebuild kit for the starter solenoid or, take it to any local auto/electric shop that specializes in starters and they can do it for you. or you can replace the starter with a new one in the reverse order of the removal. note that the starter jackshaft bolt should only be torqued to about 36 inch/pounds....just snug. you will also need to refill the pri/trans lube and perofrm a complete clutch adjustment. I recommend consulting a service manual.
hope that helps,
the test light is reacting to a bad ground and voltage bleeding through the starter because of twisting the stud on the solenoid. disconnect your battery cables ASAP.
as for the clutch cable, yes. loosen it all the way. you cannot disconnect it until you remove the primary cover, it's attached to the clutch release mechanism inside the derby cover. I don't remember the exact fill volume on the primary/transmission lube. when you go to the shop to buy it, ask them or reply to me and I'll get you the answer. you will fill through the small round cover on the outer primary with 2 screws holding it. you should replqace that o-ring as well as the derby cover o-ring. there is a gasket on the primary cover and it should be replaced.
glad I could help,