To answer both of these.
The speed issue might be a coding problem, I've started combing through the different events although I believe it's the speed not returning to normal after getting hit by an enemy. I can fix this rather easily, although I'm currently pushing for a full release as the next update. I might add some bug fixes if they get too numerous.
The bosses are the main challenge in this game. Each one is more difficult than the last although they can be stunned. The first boss can be stunned by having him run into the broken pillars all around the room. Bosses also take increased damage from the knife, so once their stunned you can spam knife without getting hit and this will take out 40% or 50% of it's health each stun cycle if spammed.
On another note, each boss has been getting nerfed. The first boss might get another damage and health nerf is he still too difficult.