Yes 300 lbs

Yes. I found a bike battery company that makes replacement battery Search for 12v bicycle battery I found them on Amazon.com about 3 places and prices. 2 batterys are from 68.00 to 83.00

i ride mine on a dirt alleyway as long as it's hard packed no issues, soft sand or gravel always a problem with any two wheeled vehicle and the small tires here only amplify the issue. I have the same issue as you I'm only 60" tall, the seat, even all the way down is still a touch tall for me, I don't know if a bike shop could fit a slightly shorter seat tube or possibly slice a small piece off the bottom of the tube for you or not....it's not unmanageable you just have to be really careful getting on and off it. When I take off I get one foot up on a pedal keep my butt off the seat and hit the throttle, once I'm going no issues, the seat is very comfy.