Okay, got past that, and to what I assume is the end (the computer checkpoint). I have a couple more notes for you now that I've played a bit longer.
The boosting mechanic... On the boost jump, I was constantly jumping late to make sure I made the hard jump after boosting, and not having enough ground after landing to hit the next jump. I went with timing the boost to run out at a good timing - which is kind of marked by the pillar in the ceiling, so that worked out. It's true that the boost running out was hard to read . Ideally you'd have a timer graphic of some sort. More importantly, your boost state persists between lives, so you could respawn and still be boosting, for instance.
Also, maybe its just me, but I liked spamming bullets in the general direction of my target when time was paused rather than aiming carefully, but they would occasionally disappear on me. I think I tracked down the reason - it seems bullets can collide with each other, destroying any that were overlapping with time paused.
Finally, this time playing it through, I managed to get myself stuck inside terrain quite a lot. Setting r to respawn is one quick fix for that. The game does have some nice mastery elements though. Knowing everything about the game, I managed to get in a run from start to finish without dying - which is pretty satisfying.