Just checked this and it looks like Unity is clamping the maximum velocity of an object somewhere in the 2D physics engine (increasing gravity works fine in the 3D physics engine), which means that the you won't be able to use 1 pixel per meter with 2d physics.
You could use 100 pixels per meter, you'll need to divide all your pixels by 100 - eg. 30, 60 becomes 0.3, 0.6.