Help,
I have no pressure to my kitchen sink/dishwasher on the hot water side. My bathroom sink, not 10 feet away, has perfect pressure. The house is nearly 100 years old, but all I can see is copper coming out of the hot water heater and copper coming out from under the sink, so I'm hoping cast iron isn't an issue. I have a single valve under the sink that splits the line to the sink and the dishwasher that I have yet to replace. Should I go straight for the valve, and check my pressure there, or is there anything else I should investigate?

Yes, that's where I would start. Remove supply line to faucet, open valve slightly to see if you have any pressure. If not change valve.