Hey there!
1+2. because of the game main design core, and the charactor is a demon hunter, so the charactor moves fast and has some movement abilities. When you use dash proficiently, it is really easy to dodge enemy attacks, which is also a core of the design. On the other hand, for balance, the cool down mechanics was added. As the game progresses, dash will help you deal with more difficult enemies.
3. The bullet time mechanics will get more reward in the future:)
4. Yes, will do this part later.
5. Upcoming more enemies.
Thanks for playing the demo and the feedback!