Mulching creates a dense mat that harbours mold, disease and varmints. I do re mow most of my clippings as they are discharged onto unmown areas. When finished, a few passes with the sweeper and Done. I haul mine to the forest nearby.
You have made a great start in overhauling your engine. You are now overloaded with information. It appears to be a fuel problem. Exhaust glowing red hot indicates a very lean mixture or Cam timing problem. Check all Fuel lines. Blow them out (cap OFF tank) outside as fuel will splash. I...