Fixable or new water heater needed?

Hot water was running out very quickly. I tested voltages, upper element looked good, on the lower the small protective plastic cover over the wires shocked me. I cut the breaker and found this loose wire. And obviously all this rust/mineral build up. If I were to fix I'd try to replace the element but I'm afraid that I won't be able to securely position the new one because of all the build up. Is that build up easy to clean off? For now, I disconnected the wires coming down from the top element and turned the breaker back on so that we at least have some hot water while we figure this out.

Any thoughts?