Ended up taking it to Rick's Automotive in Springfield at Sunshine/Campbell.
I did the after hours drop-off last night and they started diagnosing it around noon today and called to give me an update anytime they found out something new.
It's looking like it's not as bad as previously imagined, but could still turn out as the same outcome. They did a combustion gas test on the coolant and it came up clean, so the head/head gasket are fine, but they found that cylinder 3 never fires, and it's not the coil, plug, or injector. They are going to pull the valve cover on Monday and let me know if it has any obvious signs like a broken valve spring.
They've been super helpful so far, and I'll continue to update until my experience with them ends.