1998 Expedition XLT electrical/power issue

Hello from snowy McCall Idaho.
So I have an issue, and I’m going to try to fix it myself since there are no mechanics that can see it until next week, and I need my ride. Hoping it will be an easy fix.
When I bought the vehicle I noticed that the ignition always goes into key lock mode when I turn off the vehicle, and it’s a pain to turn it back on, it locks and takes a bit of finesse to get it to turn. So I was turning it off, but not putting it in the lock position. Which worked fine, but I couldn’t take my key out of the ignition. Problem one
Then three it wouldn’t start, dead battery, jumped and started immediately. I went out one cold freezing afternoon to run some errands and when I went to start the Expedition, Nothing. No click, no lights, no hum, no power windows, no windshield wipers, nothing. At the time I believed the battery to be dead, I took the battery out, charged it fully, then tried to start it again. Nothing. At. All. No power. No lights, no clicking, N radio, no power windows, totally acts like the battery isn’t even there. Took the battery out and put it in another rig, started right up. Tried another fully charged battery, again, nothing. Someone told me it might be a fuse, a gem module, something in the power distribution box. I tried to open the power distribution box but couldn’t figure out how to open it. Does anyone have any ideas?

The only thing you messed with that can cause this problem are the battery cables.

It’s not a fuse. Because when a fuse blows that’s it. It never works again.

Battery cables can have corrosion leach between the cable and the battery clamp causing a poor connection.

Tester