Normally you can access the menubar with F10. This can also be customized via gtkrc (gtk-menu-bar-accel = "whatever"). This option allows the standard menubar accelerator to be disabled.
Number of scrollback lines to keep around. You can scroll back in the terminal by this number of lines; lines that don't fit in the scrollback are discarded. Be careful with this setting; it's the primary factor in determining how much memory the terminal will use.
Sets what code the backspace key generates. Possible values are "ascii-del" for the ASCII DEL character, "control-h" for Control-H (AKA the ASCII BS character), "escape-sequence" for the escape sequence typically bound to backspace or delete. "ascii-del" is normally considered the correct setting for the Backspace key.