So your main problem is how to use your bitmap font in the game to display the actual damage? I suppose you might have heard of the SpriteFont plugin, which does a good job in many cases, but it sometimes also does crash I'm afraid.
I would suggest you do it simply with events. Using some text expressions and a comparison string it's not that hard to get a custom bitmap font working (check this older thread
When you are dealing only with numbers, you could do it even simpler. Just iterate over the individual characters, and spawn the number sprite on the respective frame.
Like that for example: DMG 135, taken apart to 1, 3, 5. Now you could just create three instances of the number sprite in order. One on frame 2, the second on frame 4 and the third on frame 6. Assuming you have your frames in order 0, 1, 2, 3, 4... which you should have of course. You have to add +1 cause frames aren't 0-based and start with the first frame on 1.
I realize this probably sounds terribly theoretical. If needed I will cook up a proper example of what I mean when I have time later.