Several of those holes are for DC volts, the top one is 6000v.

Take the leads out of the meter and let's see a photo that shows what all the holes are labeled. Looks like you have the switch set correctly, good job on that.

Looks like you had it right the first time

Right side, from the top the first three holes are all for the red lead, DC voltage. The bottom right hole is for the red lead, measuring resistance, current (milliamps), and some voltage range I can't identify without a manual.

Left side, top hole is for the red lead, AC voltage. Bottom hole is black lead.

If this were my meter and I had no manual or someone knowledgeable to ask I would not use it. Harbor Freight sells $4 meters that are likely as accurate as what you have. https://www.harborfreight.com/7-function-digital-multimeter-92020.html

Wholly crap, how the f can they design, manufacture in China, ship on a boat and then sell that for $4 and still make a profit???

Yep, test with power on.

Get an auto ranging dmm. You will have an easier time there. It sounds like the entire game is having issues. Maybe find someone local to help.
I would stop concentrating on the batteries and either focus on getting life out of the displays or getting the game to boot to a playable state like it was before you messed with the batteries.
However without the displays working it will be quite hard. You probably have a cracked solder joint on the displays. However these things can really hurt you so make sure you turn the power off before messing with them too much. A simple test would be to try to wiggle the connector slightly on the display, does it light up any more? If so then you either have cracked solder or I suppose a bad connector. I know my SBM I had to plug the connector in half way on a display before I replaced it. You could also try some sort of contact cleaner for the connector I suppose.
Of course there could be other issues on the display boards but these are the simplest to start with. If a portion is lighting up currently then start there.

I think it's time to phone a friend . There must be someone near Gilbertsville , Pa. that can come over and help . That meter - you might want to donate to a museum .

You had the meter leads correct the first time. Black in lower left and red in lower right where it says V-Ohm-ma. That is for normal DC voltage within the range of what you can use on the dial. The others are for high DC voltage where the input goes through some voltage dividers so you can measure higher voltages without wrapping the needle around the peg. Best for a beginner to get a digital volt meter to eliminate some confusion.

That time was back on page one. C'mon Pinside.

Any job is easy with the proper tools!