I’ll start with #3&5. If your cooling system is working correctly check the vents in the lower fairings, they control airflow into the cockpit area. I never had leg heat issues on my 1st gen.
I haven’t seen much luck with a single carb swap in the posts I’ve read, get the carbs right and keep em clean and that thing is a rocket.
I’m sure some of the 1st gen gurus will be around soon to give better info, I’ve moved to a 2nd gen as I like feet forward bikes.
Welcome to the site, you won’t find better info anywhere to keep her going, best $12 investment you’ll spend on the bike.
I suggest you ask over in the Watering Hole or 1st gen sections to get better response.