Won't turn on, is this corrosion on my logic board / is it fixable?

Macbook Air 11-inch (Mid-2011) [A1370]

Hello everyone,

I will try to make this as clear and concise as possible, as I know troubleshooting with incomplete information can be frustrating. Basically my MBAir won't turn on anymore out of nowhere, no liquid spills or physical damage/drops ever. The "Observations" below are things that I noticed while troubleshooting and results of the "things I tried".

1. Does not boot, no chime, no fans spinning, nothing on display. Only a faint "zzz" sound that lasts 1 second (see below for details)
2. A couple days before it died the screen became briefly distorted while watching a Youtube video. Not white horizontal lines or black bars, I mean the person's face and body was zig-zagged along with the rest of the scenery in the video. Like you see in movies when someones computer screen gets hacked or glitches. That went away after rebooting and worked fine for a couple more days.

1. Took to apple store, they said it's a "legacy" laptop meaning its too old for them to take in and diagnose.
2. Replaced original battery [no boot]
3. Replaced charger and also plugged in at Applestore [no boot; light stays ORANGE]
4. Disconnected and re-connected battery [no boot]
5. SMC resets (with power connected and disconneted) [no boot]
6. Opened bottom plate and cleaned all dust with brush, compressed air and vacuum [no boot]

1. Pushing the power button (charger unplugged) makes a very faint and brief (~half second) spinning "zzz" sound near the top-left side of the keyboard where the fan is located. Holding down the power button makes the same half-second sound every 5-6 seconds (i.e. holding the power button for 15 seconds, I can hear the "zzz" fan sound about 3 to 4 times).
2. Power button (charger plugged in) does not make any sound when pressed; instead the "zzz" sound reoccurs by itself every 5-6 seconds as long as the charger is left plugged in.
3. Performing SMC reset with magsafe connected turns the light from ORANGE, to GREEN as soon as I release all keys, then back to ORANGE two seconds later. Still no boot and same fan sound is heard.
4. While cleaning I noticed white (corrosion?) marks on board and metal things that stick up, near the magsafe jack (see photo). Could this be the culprit? If so, can it be cleaned to work again, or is it not even worth trying to salvage?

If there's anything else that I can provide that might help solve this problem, please let me know. Thanks in advance!