I don't want to cook 6 lbs worth of meat, so I'm thinking of just using 2 lbs. Would this affect the cooking time in the oven? Also, is there a d...

I used a 2.7lb thin piece (approx 1 inch) and it was perfect in 3 hours simmer time.

I used a 3-lb. corned beef a couple of the times I tested it, and the recipe divides very well. The simmering time depends mostly on the thickness of the piece of corned beef you're working with, as you mentioned, which can be similar whether you're working with 2 or 6 pounds of brisket.

So if it's a skinny-looking point cut piece that tapers into a thin triangle (about 1-1.5 inches thick, like the one in the recipe slideshow) it very well might need only 3 hours of simmer time, so just check it for tenderness early (and it should hold well between the simmer and bake stages if it does finish early).

As for the chile -- the flavoring is subtle, so you can substitute any other small dried red chile (or skip it, without ill effect).