there is one other thing beneath the bridge you can use
O H
Wow I feel kind of foolish now haha
I'd tried dying before, but I must have gotten the X and O buttons mixed up because I only remember resurrecting once, and I hadn't even noticed at the time because at that point I'd tried replacing the vine all over the room, and that time I'd placed it right at the lever...
Like I said, I could slap my own forehead :P
Anyway thank you for being so patient lol you really tried not to spoil it for me and let me figure it out with your hints (I appreciate that!)