I used one Heart at the start of this round, so I could have had 57 if I didn't mess that up.
Ah-ha! I figured out a trick to getting a higher score.
The "spreading" enemy doubles itself every 3 turns, and if you kill one part of it, it drops a random piece. If you wait until the late game and set one loose, you can get more drops so long as your Swords and Spades are sufficient to clean up the ensuing mess.