You can easily make it get hurt by explosions by adapting the hitpoints routine from mouser. Then put this code in place of where it says increase hit counter.
Change where it says hitpoints to something else like hitpoint. Then paste this somewhere in the main code or something.
LDA $1564,x ; if invincibility timer isn't active,
BEQ JUMP ; go to hitpoints routine
DEC $1564,x ; else, decrease invincibility timer
JUMP JSR HITPOINT
NO_JUMP JSR SUB_OFF_SCREEN_X0 ; only process sprite while on screen
JSL $01A7DC ; interact with mario
Then where it says SPRITE_INTERACT change that whole code to RTS. Now your sprite should be hurt by bomb explosions.
Edit: actually I got this from the thwomp boss hitpoints routine, so you're probably better off adapting it from that.
Also shut up.