I'm having an iMac backlight problem

@thechain this "shine a flashlight on the screen I get a faint picture" sounds like a LED driver board issue. I'd consider this "hooking it up to my television today. Nothing. " a red herring for now. Check your LED driver board by taking a good look at it and see if you find any components that appear damaged etc. Use this guide iMac Intel 21.5" EMC 2428 LED Driver Board Replacement to work on it. You can of course also post some images of your boards with your question so that we can see what you see in case you need more help with that. Use this guide Adding images to an existing question for that. Bottom line for me is to replace the LED driver board and see if that brings your iMac back to light.