That stuff in fuse blaock looks like corosion or a short from circuit or water leak on it.. See what those fuses feed and yes obviously clean it. Silicone grease doesnt corrode. But as far as the rest just as I had said check all grounds. They will wreak havoc on the system as u saw. As far as alternators as I had also said previously that ones from stores or online are horrible quality and dont last, when mine went I had only changed bearings, as voltage reg either works or it doesnt and if theres enough length on brushes dont change them ,and as long as slip rings are good then your good to go. Anyhow glad you found it Good Luck

 

I have a long term update on this issue. After cleaning grounds the alternator has behaved well, but ended up with intermittent OD Off light and limp home shifting.

I was able to pull the transmission code using FORScan and a cheapish dongle that they recommend.

The odd shifting issue ended up being the EPC solenoid in the transmission. Probably related to the electrical failure. This video is for a Mazda 6 but the troubleshooting I ended up doing is the same at the transmission: