Sorry! something to note is that you can refill your 02 Gauge by interacting with the canister, we didn't really make that clear, in my eyes you beat the game! thanks for taking the time out of your day to play it!
So, I returned to the game and this time made it to the end!
I have to say knowing that I can resupply with oxygen really turned this game around for me. Now I could explore the ducts AND leave for a resupply when needed. This created some really tense moments where I wasn't sure I had enough air for a return trip, and in the end I had to rush blindly forward in hopes of reaching the end this one time, and it turned out the right way, I jumped down and scrambled to the canister - this felt really great.