1) You forgot to initialize the font addon. Initialize it before you initialize the ttf addon. This is why it is crashing.
2) %lf is the correct printf format specifier for a double, not %d, that is for signed integers. Note : After messing with al_draw_textf for a while, it does not recognize %lf as a valid specifier, even though printf does. Use %f and cast fps to a float.
3) You're waiting for events twice, get rid of lines 102 and 103.
4) You're drawing the buffer on top of the FPS counter, so you'll never see it. Swap lines 119 and 120.