Unfortunately the kayak is not built to hold that additional weight, it can take only up to 325 lbs. However normally 10 foot sit on top kayaks are not meant to accommodate trolling motors.
I can tell you I do not think I could stand up in this kayak. It is really not very stable. It is good for what is built to do, navigate skinny water. The seat needs to replaced as it is very uncomfortable and has 0 back support. There are much better boats for a little more money, try the 3 Water's Big Fish line. Great seat and much better stability
Nope
You'll have to buy something after market.