I really enjoyed this game Jason. I thought the tutorial level was certainty useful to start given the variety of mechanics you needed to introduce and I also appreciate how you included the text instructions. In regards to the difficulty, I do not think it was difficult. Initially when I started I was mashing the I key to get a higher Rocket Jump but I later discovered that if you press I and W at the same time it will give the player a large boost.
In regards to your question about horizontal dash, I do think it would be helpful to dash horizontally after jumping as that would allow the player to jump to farther away platforms more easily since they already get a boost by jumping in the air.
I also like how you changed up the music each level(the music all of a sudden got serious at level 2) and how each level had its own color scheme. The little particles that come off the player after changing levels is also a cool effect.