I am trying to help, but have you read my post #15? The regulator system if working correctly, regulates IGN circuit voltage to 13.8V at about 68F, it will go a few 0.1V higher when colder and lower when hot.
A battery voltage over 14.5V is too much, and suggests voltage drop problems. The field of alternator is controlled by the regulator, the regulator senses IGN, but with voltage drop the battery voltage will run higher, by the voltage drop between IGN, and battery. If 18V, was measured at IGN, that may suggest the regulator is stuck, and may be providing full field, however drops to 7V, suggests poor connections. This means there is likely more than one problem.
