Spilled water, no power, corrosion under cpu?

Hello, about 8 months ago my cat spilled a glass of water on my Macbook pro Retina A1502. I wasn't home at the time but my wife immediately turned off the power and flipped it upside down. After leaving it in rice (I know now it doesn't help) for a few days I tried to power it up but got nothing. I took it to a local computer shop and the guy basically told me I was a moron for trying to turn it on at all, he opened it up unhooked my battery and told me to take it to someone to get an alcohol bath. At the time I thought it was toast, didn't have the tools to even open it up and it has been sitting since.

Fast forward to the present I decided that whatever's wrong with it should be fixable, ordered an ifixit basic tool kit and I followed Youtube tutorials on how to disassemble and look for signs of corrosion, which I've done today. The water indicator spot was not red.

My question is: after taking out the logic board, I found a big spot on the bottom, right under the CPU. The rest of the board looks perfect. Is this my problem? is my CPU toast? can I just clean it up with isopropyl and a toothbrush?

I am thinking of ordering a new keyboard as well because I've read it can be a common problem after water spills and it's pretty affordable.

Thanks for reading.

Update: I cleaned up any possible spots I could find on the logic board, reinstalled everything, plugged the battery back in and the magsafe, still no power. Magsafe is green when battery unplugged and orange when plugged. Here's the spot where the corrosion was after cleaning:

Also noticed some weird discoloration on the IO board, is this normal?

Decided to continue the tear down to see if there was any corrosion in the keyboard, currently have the battery and backlight off, here's what it looks like: