Won't Charge, Won't Turn On, But Trying to Retireve Data

A couple of years ago, my grandmother turned her RealPad over to me to "fix". Apparently, it wasn't charging or turning on. This wouldn't be a problem, if it didn't have a picture saved to it that she desperately wants. My first stop was AARP's website to try the Customer Service route, but it looks like that's no longer available. So far, I have tried cleaning the charging port, using a newer charge cable, and plugging said cable into a wall outlet as opposed to a USB port on a computer. No dice. I lack the know-how and tools to be able to tell if the battery is dead, or if it's a much bigger problem. Does anyone have any advice on how to either 1.) diagnose the problem with more accuracy, 2.) retrieve the data off of the tablet without repairing it, and/or 3.) locate a replacement battery for the retched thing?

USB ammeter came in today. I tried both the cable that my grandmother was using and an old phone charger cable. I had to use said phone charger's plug as well. I must confess, I'm not as well versed in this stuff as I should be. So I had to look up a Youtube video on how to use the USB ammeter. I think I got it right.

Above is the reading for the original cable.

And this is the reading with the phone cable.

And this is the back of the plug (forgive the blurriness). I believe it says 5.1V (which is standard, if I recall correctly).

I unfortunately have never owned an iPad, but I did have an old Barnes and Noble Nook charger and a more newish Amazon Fire HD 8 charger.

Above is the Amazon Fire charger.

And here is the Nook charger.

I would say by the numbers that the Fire charger has more oomph, but neither caused the tablet to either pop up a charging screen or come on. Should I try leaving it plugged in overnight with either? Or is it autopsy time?