How Fast Can A Fusion Powered Spaceship Travel?

Assume the spaceship has mass M, and the the fuel has mass m
The spaceship has a fusion powered engine.
1) How much energy can you theoretically get out of the fuel using fusionpower?
2) what is the fastest speed the spaceship can reach using the amount of fuel m, and how long time does it take to reach it?
2) Assume the spaceship accelerates with 0. 5g. How long does it take to burn of all the fuel and what is the velocity at that time.