I am glad you are enjoying the game!
When it comes to the waiting at the door ending, it's more so just a secret that I put here because I thought It would be cool more than anything (There will be a whole new zone there in the future and a bossfight)
When it comes to the new item, I did not really add functionality to it because I wanted to release the v2 update already without endlessly adding new stuff, I will do something in v3 with it.
When it comes to v3, I did not start making it yet, but I want to add something like a hard mode with a lot harder stuff, some of the obstacles will be from old unnerfed unreleased versions (which were pretty insane difficulty wise).
There are three endings in the game (waiting at the door is more of a secret since it doesn't delete your save file and it doesn't show an endscreen), I am really impressed that you managed to find the third one (the one with the 3d pyramid guy), good job!
Also, damn you are really good at speedrunning this game, I would really like to see your runs, so if you want to, be sure to post them on youtube or something