The 13" model DOES NOT have "RadeonGate" problems (it has an integrated GPU).
That IS NOT your problem.
What I'd try:
You'll need to take the back cover off.
You need a Phillips #00 driver to do this.
Take note of where the "longer" screws go (so you put them back into the right holes).
I'd try removing the RAM, and let it sit for an hour or two.
Then I'd put the RAM back in, put the back cover on, and try again.
BE CAREFUL when you remove the RAM. It's held in place by "retainer springs" that can be fragile and are easily broken. Again, use care when spreading these apart so that you can lift the RAM dimms out.
There are "PRAM" and "SMC" resets (sorry, I don't remember the key combinations).
I'd try both of those, as well.
Were you having the problems with charged connected, as well as disconnected?