Nice game! Has potentoal to be casual mobile game too. You can welcome speedruns here just by adding a timer. I can finish a level quickly by jumping directly to the exit if I'm skillful enough to click on the right angles at the right time.
About the hold fire for higher jump, I think it doesn't work. I just got lucky to pass that level by spamming clicks. Repeatedly dying until it sent me to the flag while spinning. Haha!
Suggestion: Add a short line that indicates the aim angle. That way player can easily visualize the trajectory of the next shot.