DO NOT restart the engine, even for diagnostic purposes.
7000 miles since the last oil change, sludge on the dip-stick, burnt smelling oil, hammering noise at start-up followed by squealing sounds. This all tells me that the engine is about ready to "throw a rod".
Pull that engine NOW! If that engine lets loose while you're doing a diagnostic run, you just got a boat anchor instead of a possibly rebuildable engine.