When you first start it in the morning do it miss on one cylinder for a second or two then clear up and run fine after that. Mine did finally pulled the injectors after it wouldn't crank over after stitting a week or two and #3 cyl was filling with coolant. pulled head and had pressure check and head is cracked or bad casting in the the outside intake runner of the head,blew water everywhere. And yes it is a job to pull the head. Currently looking for an engine because #3 liner is damaged.

Your #2 comment makes me wonder if you have a bad radiator cap (on the CRD the cap on the plastic reservoir) that's bleeding pressure too early and allowing too much coolant to flow into the overflow side of the tank on a hot engine. I don't know if the cap can be checked but a new one is cheap enough to just purchase and put on to see what happens.

If the combustion leak kit doesn't show anything try adding the appropriate UV dye, parts store should have, to the coolant, drive a bit and then use a UV light, parts store again or Amazon, to look for the leak. This is good for detecting tiny leaks and ones where the fluid drips to a hot surface and immediately evaporates. Years ago on another vehicle this method found a really tiny leak at a lower radiator hose fitting that wasn't tight enough.

There has been at least one report of detecting a water pump leak by looking up at the front passenger side of the engine, with the skid off I suspect.

If you changed your tstat recently there has been 1 report of a leak due to a stripped lower rear bolt, the one that's impossible to see well or get too without a long 1/4" wobble extension.

EGR coolant pipes?

I am once again dealing with a glowing low coolant light on my dash.

Have any of you encountered this issue? Could you shed light as to what maybe happening?
Tomorrow, I pick up a combustion leak detector kit from the auto parts store and I’ll report back.

Any ideas?

I have seen this on other vehicles too. I suspect it is the shaft seal on the water pump. Depending on where the seal stops, it leaks or it doesn't.
Possibly leaking when the engine is running and that is why you don't see it.

Do the dye and then check.

I don't see how combustion gases can escape through the head gasket into the coolant and not register on a CO meter unless it is not working..

With your header tank "pressurizing", it is hard to imagine where the pressure is coming from other than combustion gas.

If combustion pressure is getting into the cooling system, it would easily overcome the capacity of even a brand new rad cap and blow coolant out the overflow.