Are you using HD video (component cable and HDTV settings)? from here: Some Virtual Console games default to displaying 240 lines of video. Some HD TV's are unable to display a signal with only 240 lines. Try the steps below to set the Wii to output 480 lines of video, which may solve the problem: (1) While on the Wii Channel Menu (main screen of the Wii), connect a Nunchuk to Wii Remote. (2) Select the Virtual Console game from the Wii menu, then select "Start" to begin the game. (3) When the game starts, press the Home button on the Wii Remote. (In many games, the music can be heard when the game starts.) (4) Select "Operations Manual" from the Home menu. (5) Press the Z + A + 2 Button simultaneously (the Z Button is on the Nunchuk). A sound will be heard if the button combination has been entered correctly. (6) Close the Home menu. The game should now display correctly. Note: You will not have to do this the next time you play, as the Wii console will remember these settings.
I searched a little and discovered (from apple technician guide) that keyboard and trackpad are connected to the cypress PSOC 24794 that provides an USB interface. Looking at photos on iFixit guides I can see that PSOC is soldered to the logic board. So I'll have to build a usb controller (maybe using the same PSOC model) to make it work. Better to sell the top case and get a usb or wireless keyboard!
The problem is the controller on the logic board that's SATA II (3,0 Gb/s). Maybe a SATA III (6.0 Gb/s) cable are better shielded and you can gain some speed, but you definitely cannot achieve SATA III speeds.
It seems to me like bad RAM. (I assume you know that it must be 2x4GB modules and not a single 8GB, and that you double checked that they are correctly installed and are the correct type that your mac can accept). try to swap only a module at a time to se if it's working. Where did you get it? I bought 4+4GB from crucial a year ago, and everything runs fine.