I would bypass the seat safety to test if the new safety switch is bad. You should be able to run a jumper wire between the wires connected to the switch.
A friend dropped off his Cub Cadet XT1 with Intellipower to get running with crank no start. After I drained the overfilled and extra quart of oil (not overly thin or gassy smelling) and changing his "new" spark plug which was oil fouled it started but ran weak with lightly black smoke. Owner...
It looks like the governor weight or weights split at the faster that attaches it to the governor gear. I highlighted in a photo of the governor gear where the curve of the piece matches your part. I theorize that this could be from one or both weights splitting. I scanned the parts diagram at...