from your description that it overheats, had smoggy emission, and low oil level it seems that your engine is suffering from blowby, your piston rings are worn, your oil and air/fuel mixture manages to pass thru your compression and oil scraper ring hence smog, high oil consumption and overheating. If you pull one of the vent hoses i'm sure you would have lots of air coming out because of loose compression(positive crankcase ventilation). It wont turn on because the cylinder pressure is too low to support combustion or your engine could have SEIZED. YOUR ENGINE NOW NEEDS A GOOD MAJOR OVERHAUL.