If they were set up in an array the short bursts could be as continuous and powerful as the hardware and power source could handle. Theoretically.
Yes, and the inherent problem with fuel cells is that they cannot change the amount of energy they are generating very quickly. If you put one in a car with a these new batteries, you could have the power output set at a mid range and you could run off the batteries practically all the time, charging when cruising at a steady pace or stopped and discharging when accelerating. Great for around town.
Might even be nice for a Bonneville Salt Flat run.