I am honored to hear that I helped give you motivation to work on your game! I wish you the best of luck and hope to play it when it releases!
I think you needed to talk to SCP-166 more as that triggers them to open the door covered in grass to the right of the room. From there there are more levels and you get to meet BIG SCP-610 again ;). I just uploaded a newer version of the game right now! I overhauled the entire GUI for the game and re-did some sprites! Also I added a new intro cutscene animated by one of my friends. (He is in the credits page!).
Also yes there is one more weapon to find!!! And thank you for the feedback it has been very helpful!!