Thanks for your feedback. Your are right, the slowdown disables when you use your grapple. This is intentional. We wanted it to have a feel like the game "superhot" where time slows down or stops when you are not moving, but when you move, time moves too. We think the game would be too slow paced, easy and boring if you could slowdown even during the grapple.
Glad that you got to the last level. That is our only combat focused level, so I am glad you got to play it, but it is difficult for sure. What did you think about the pull and throwing the bullets mechanic? Did it make sense to you?