Your firewall is not cracked or brocken. That's where much of the ware on my floor came from, a cracked firewall. NOT GOOD. I was going to try to replace it a while back then I said what the hell it's an '84.
One more thing the E30 should have a seal that goes around the upper rim of the hood, directly above the firewall in fact if that's not present then water could be seeping in there, not good potential rusting.