Well apart from Chromium you're relying on a closed source "stack", I'm not sure it's pretty secure. You didn't mention it, but you should revert to a clean VM

Well apart from Chromium you're relying on a closed source "stack", I'm not sure it's pretty secure. You didn't mention it, but you should revert to a clean VM snapshot after each time you use your VM (like they do in Qubes).