I managed to beat both Level 8 and 9 without cheats, but I can't say that I didn't die at least twice in each level. If you're looking for blue bubbles, walk through wall downward right of the "triforce" room. However, since you express concern about the difficulty, I will tweak it.
Most of the difficult fights can be avoided if you have enough keys, or have the magic key.
EDIT: Made some modifications to Level 9 and decreased the damage and speed of L2 wall masters in Level 8.
Tell me if this is better.