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Regarding your seat, I believe you could use a 1-inch spacer on each side so you don’t have to bend anything. Check out ShopAKR.com to find the right size spacers you need. Be sure to use washers large enough on each end as well.
You have two choices. You can use a heavy dead blow hammer (my choice) or use a bent axle or jack handle to pry it. Easiest with the kart on the ground for leverage and you can stand on the opposite side. Majority of the bending should be on the left strut to avoid engine clearance issues.