I could have sworn it was just 2 bolts holding mine in when I had it out, there was the harness electrical connection and the big wire
bolted one on the side. Mounting bolts was one that had the electrical connector harness bracket and the bolt right BELOW that one just like shown in your picture. I still think the issue is all that corrosion on the lower bolt, you obviously have an electrolysis problem causing the metal to decay like that.