Help! I need a new e-bike! I need help in resolving two issues.

Check out the Dost Drop. It’s a step-thru, mid drive, with throttle! Schwalbe tires. A very nice bike.
New models with CVT and belt drive are sold out already. But Drop is arriving soon they say.

if you need a bike shop for support, look at Gazelle C380 or Trek Allante 7.

I doubt you’ll find many step thru ebikes that are not Class 1. The step through frame is typically not strong enough to support Class 3 power and torque. Hence the stagger frame was created.

Most batteries are warranted for 1000 charges. Even after that, they’ll still charge and run around 75% of original Specification. But it’s important that the battery cells are high quality eg Panasonic, LG, and Samsung.
Late top the discussion, but you can put all those tire fixes on your present ebike. Personally, I don't know if I'd care for the feel of semi-solid inserts in my tires, or the extra weight.