Hi Lakeman, Welcome. fishing lakes is a bit different from fishing rivers, but equally good fisheries.

You are right, the corn will get washed downstream, but the carp will be on the move looking for the source of the bait. You will have to chum a bit more than you would in a lake.

Yes you can use your #4 hook with corn and do well, Though the hair rig really is not as complicated as it seems. I'm living proof...If I can learn it anyone can...And yes it is worth the try.

Fish the river almost the same as you would a lake except use a sliding sinker (egg type or similar) 1-2 oz. so the cuurent doesnt move your rig around. I find in rivers around here you dont have to cast far, as the carp usually feed on the edge of the current. In Pecatonica River I'm usually only 12-15 ft. out. Bigger rivers will be farther.

I would recommend using no less than 12lb. test mono. My personal prefernce is 50lb. PowerPro braid. It has a diameter of 10lb. and has zero stretch and is very sensitive. But to each his own.

Yes crimping the split shots onto your line will weaken the line in that spot considerably. When you tie into a 20-30lb. fish you will want every bit of strength you can get, trust me! Try using a barrel swivel instead to seperate or create a stop for your egg sinker.