It's not the ignition coil. The coil has nothing to do with running the starter.

I was gonna have you clean & tighten the OTHER END of each battery cable, because it almost sounded like a bad connection there. That's easy to overlook, when you're cleaning & tightening the cables at the battery posts. But that doesn't explain why your battery voltage drops low.

You say your battery measures 11.8v when you tried to restart. Do you mean while you turn the key to start? Measure the battery voltage just before & continue while you turn the key to start. What does it do?

You mention it clicking but not cranking. Where is the clicking sound located? If it's at the starter (my guess), then it's likely a bad starter solenoid. Maybe you can get that by itself, but usually it's just part of the starter.