Glad to hear you got the z-axis problem straightened out. My response was already quite long, so I held off on the Repetier-Host suggestion for a later post if it was necessary. I haven't used RH for over a year, but I remember the eeprom view built into it being pretty slick.

You are correct that the LCD isn't required for printing. I've known MakerFarm owners who even removed it from their printer. There are non-MakerFarm printers that don't have one to begin with. IMO, running without an LCD is especially possible when running RH as host software. Slicer capabilities drove me to Simplify3D instead of RH/Cura; I still miss the printer control capabilities that were provided by RH.

Can the display gibberish be at least temporarily fixed by restarting or resetting the printer? If it is a permanent problem and this is still an LCD with two ribbon cables, I'd try switching the two ribbon cables going to the display. I don't think crossing the cables can lead to gibberish, but a bad connection on a pin of one cable might. Seeing what happens by switching the cables might help reveal whether there's a cable problem or some other issue.