Then you would move basically at the speed of light.
A rocket in vacuum doesn’t “push” off of anything. The directed expansion of gases causes the system to expand linearly in both directions. The rocket goes one direction and the gases o the opposite direction. In days of old when there was no concept of vacuum and it was supposed that space beyond the atmosphere was filled with a substance termed ether then it was believed that push was the operating force.
The Em Drive will work if and when it is understood and demonstrated how it maintains conservation of energy. Changing the laws of nature may not be necessary, just understanding how something works pursuant to those laws of nature. I don’t count on this thing actually working. The reasoning for it sounds like the reasoning of yore that showed scientists how to build perpetual motion machines or that posited ether.
Not really because the EM Drive generates only a small force.