Hi and welcome to the Forum and to the Cub Family
You should be able to remove what is left of the main metering jet. Probably a little patience and a little ingenuity.
Some of the pro's should pop in and may have a pet trick on how to do this.
In the meantime, might I suggest that you read the sticky - New Members and Guests Please Read. It will provide you with tons of information for FAQ's to Manuals and Serial numbers and Paint Codes.
As far as the TOB and the pressure plate - check what it says in the Blue Ribbon Service Manuals.... if your TOB is badly worn, cracked, chipped or excessively dry from lack of lubrication, then that would probably be a good idea. Also, you may want to stick with the graphite one from YOUR DEALER, and leave the aftermarket and Bates alone. There has been many posts on this particlular subject.
Hope this helps some.. again welcome to the Fourm