Opening the inventory and clicking on the "settings" tab will give you access to volume controls ^^
I'm able to tab out of the game without issues with alt+tab, could you explain what happens for you?
Ooh you're probably playing the Itch.io version! This one is old and didn't have the volume sliders. They've been implemented in the newest one.
Mmh... I don't know what to say about your keyboard being locked though, I can tab out of the game just fine, but it's a bit worrying for sure. I'll take any info you have! If I can understand what's happening, I might be able to fix it in a future build ^^