As for Page↑/Page↓: 1680×1050 here. Could reproduce it in both Firefox and Chrome.
As for dead keys: It may require rethinking input handling, depending on how you're doing it currently. Input is usually on two different levels: Key presses and text input. While you usually cannot reliably turn the former into text and cannot get a pressed key from the latter (could also have been an IME or multiple keypresses), you usually should be able to handle a key press (for opening the console) and not have it result in state changes for text input handling (which would be required for input on the console).
Feedback button now works, but didn't for me when I wrote that comment either on Firefox or Chrome on Windows 10. I didn't consider checking the dev tools, though, sorry. But seems to be resolved now.