Something else you might try is to put the printer into hex dump mode, you press some combination of buttons while turning the printer on to make sure the right escape sequence is making it to the printer.

>1. I think the LQ-300+ has the fonts built-in as I can select those fonts by pressing some hard key combination on its panel (It means the hardware control of fonts works) and there are a font list on that panel too. I remember I checked its PDF manual but it seems does not mention the code for each font. Only know the LED 001 means Draft, 010 means Roman, etc. printed on the panel. I will check the manual again to see I missed it or not.