Couple things come to mind when I read the original post.

1st is that thermal shock is the kiss of death for head gaskets. In the specific case of our poorly cast block, it could perhaps cause the block to crack more easily than it would in most any other motor. Still my knee jerk answer to what the cause is when overheat has occured is "head gasket failure" via warping of the head etc.

The answers to your first to questions IMO:

1. No, It may or may not be fixable even if you do pull the motor. Many will argue about if fixing a cracked block is possible, it is possible but it may not be worth while. Thus I haven't started to look at my cracked block yet, though I probably will take a stab at it because I've nothing to lose. You have a 2003 which like my 2004 is unfortunately very prone to block cracks. You do NOT have is a slipped sleeve! Our years have revised block design with a lip that captures the bottom of the cylinder so it can't slip downward. However, it doesn't mean that the block behind the cylinder wall can't crack, which is what mine did.

2. No, not in any likelihood. It is theoretically possible but the area it has likely cracked is not going to be visible until the heads off, furthermore the issues that arise from a HG failure are in many cases the same as a cracked block though not always.

Red5/Dave03S gave you pretty sound advice. I would absolutely follow both those tips.

Pulling your spark plugs will pretty quickly tell you if you've got water in your cylinder, it's going to effectively steam clean the spark plug. If one or two look VERY clean compared to the rest, I'd certainly investigate further.
I used a USB scope off amazon that I bought a few years back for $15 bucks with my phone, it works on a laptop too which was nice with a bigger screen. I found it slightly challenging even with the built in light and 90* camera mirror on the end to be able to differentiate with certainty, the contents and condition of the cylinders. I could tell that one cylinder was very clean and it was a middle cylinder which I knew was a bad sign since it wasn't by a water jacket. I could not tell if I was seeing coolant or oil by camera in that cylinder and in all cylinders, detecting liquid was challenging though I could read the details and texture of the piston quite easily. Cylinder walls were hard to examine due to light reflection but I didn't see any issues and later I found out they were perfect. If you use a piece of white paper towel or similar you can quite easily spin it into a rod and use it to dip against the piston. Turn the motor over by hand to push the contents up if you need. In my case, I found no oil but just bright green coolant on the paper towel, I knew I had a heavy coolant leak. If for some reason you can't do what Dave explained, this would be my next move.

 

I pulled the cyl 4 plug this weekend. It was not properly gapped.

The plug tip did not look stream cleaned. I pulled cylinder 6 plug and it looked the same.

I looked in cylinder 4 with borascope and I couldn't figure out how to bend the camera upwards to view the seam between the head and block. I could not tell whether the cylinder 4 or 6 looked steam cleaned from the piston tops and cylinder walls.

I swapped the plugs between Cyl 4 and cyl 6

P0304 - Cylinder 4 misfire seems to have gone away. I did not get P0306 - Cylinder 6 misfire.

I did continue getting P0150. So I will clean Bank 2 front sensor this weekend

I saw another freaky code for the first time P005d - Cam B something or other. Anybody ever get this? What is it?