Despite my pc definitely being far beyond the requirements for this game, it still wouldn't go beyond 44 FPS for some odd reason.
I was able to fix this by opening another application/window (I used task manager) and just click on that window to "focus" on it instead of the game. Every few seconds it would hit 45 or 46 fps and move me forward a notch. That's the only way I could get it to move forward.
Once you move forward towards the boss, you will have to defeat three guys. Once you are at one of the characters, Just click on the window and drag it around (but not excessively to trigger the cheat) and that will cause the game to lag, which will damage the bosses.
Have fun!