What did the old spark plugs look like? Your #5 cylinder is significantly lower than the others. I would suspect that the old #5 plug would have looked different.
You need to find out why the #5 cylinder is lower in compression. If you squirt a tablespoon of engine oil and do a new compression test, and the number comes up, it would indicate a problem with piston rings. If the number stays the same, you likely have a valve problem. Either a burnt exhaust valve, sticky valve guide, or the rocker arm is adjusted too tight. Do you have hydraulic lifters? You might have a dirty/bad one.
Carl
