Take some time to explore a bit on your first few runs. Between hidden walls and hidden power ups there are many easy to miss things that familiarity with the stages will bring about.

Also, you want to get good at maintaining the fire ball power up, as it is easily the strongest, and most effective weapon in the whole game. If you do not have that by a boss fight, the boss fight is likely a loss of time.

Game is still being routed from what it looks like, so its awesome to get another set of eyes on board with figuring out where to make cuts on time.

have fun.

Holy cow, I never thought to use grenades like that. Maniatikiller, you just opened the door to break the 20 minute mark on this game with your submission, that is awesome!!

Its timing. If he is at a certain point on his loop, and has a certain amount of HP by the time he repeats, his pattern changes. If you hit him down to one point above his threshold, he will repeat the loop giving you enough time to finish him off.