Truck won't start after plugging in DC radio at cig lighter

Truck never had problems starting. Alternator is fairly new.
Battery is only 1/2 yr old. 610 v/or amps
I plugged a Sony shortwave radio into the cigarette lighter slot, ICF-2010 (which has a 4.5V DC in). The radio had Error 3 when using regular batteries. So I purchased a DC Car Adapter/charger which outputs 5V / 2A. Plugged it into the cig lighter and the radio for about 2 min. Radio did not show any error, but it also did not show anything, as if it was off.

Next day, I got in my truck, turned on the key to roll windows down. They rolled down, but when turning the key to start, the engine didn't turn over. All I heard was a 'dead' click. Then the windows wouldn't go back up again. Completely dead.

I got an old Sears battery charger and put it on the battery at 10Amps for about 1-1/2hrs. The truck only started after that when placing the charger at 50amps (Jump Start). Truck started, and I left it running in idle for about 30min. Turned it off, and when trying to turn it back on, same thing as before, dead.

Took the battery to Autozone, and they said battery was at 89%. They charged it to full afterwards. I have not installed the battery back since then, since I don't know what is draining it.

What can I check (with voltmeter, etc) before I take it to a mechanic? Not that it has anything to do with it, but I am a female and ---I am not 'auto repair' inclined; but I could try checking a few things. I suspect a fuse, relay may have blown? Maybe the radio has a bad capacitor which drew too much current and blew something in my truck? I hope nothing major.

I appreciate any help you may offer.