Howdy y'all, I'm hoping for some diagnostics help to decide what to do, the car has 270k miles and I'd love to extend it's life further...

The engine starts up fine, but seems to be struggling idling and accelerating, then it stalls out, anywhere from immediately to around a minute after starting. I'm getting misfire codes P0300, P0302, and P0306, as well as P0171 and P0174.
After stalling, these lights come on:



While driving, its just the Check Engine Light and VSC that are on....
A similar issue happened last week where I was getting codes for cylinders 3 and 4 instead of 2 and 6, while still getting the random misfire codes and the lean mixture codes, however, it wasn't stalling, just running rough. I changed the spark plugs to try and remedy that issue, and it worked, the car ran smoothly for about 250 miles with no codes and a cleared CEL. All of a sudden I noticed a sluggish acceleration, and then the engine began to stall as described above...

I was able to slug it home, and noticed there was a slight fluid leak, is it possible that something is leaking into the cylinders? The valve cover gaskets were replaced about 50k miles ago. Could it be that? A different kind of leak? Bad coils? MAF Sensor? IACV?

Here's a picture of the engine, it's not the best photo, but you can see that there is some slight fluid buildup near the bottom of the engine, it's not enough to create any oil puddles under the car however...

Please let me know what you guys think... I'd really like to DIY it if possible, depending on the job and it's complexity.