Sacred Redstone

Not too sure what you mean by "gamemode menu". There is, however, a shortcut to switch between creative and spectator mode, which is F3 + N. In your case, it would be Fn + F3 + N.

Check your mouse sensitivity setting. Look under Settings > Controllers > Mouse settings.

The server list is not stored on your account, it's stored in your minecraft installation folder. The name of the file is "servers.dat". 

 This isn't a bug. Soul sand might appear to be a full block, but it's hitbox is actually one pixel shorter, meaning entities like players, mobs or items will sink down in into it by one pixel. The problem here is that the items are being caught on the edge of the hopper. To fix this, move the hopper line down by one, and stop the water using signs placed along the stone.

If you wait at least 5 minutes (may be longer if the game is running very slowly), the items should naturally de-spawn.