No Hot Water in Kitchen Faucet, hot water runs to dishwasher but not to faucet
Disconnect the flex hose from your hot supply valve to the faucet and test for flow with the faucet disconnected. Ideally you do this with spare 3/8" hose, but a towel, sponge, bucket, and some care will also work.

If your unconnected valve supplies decent water flow when disconnected from your faucet, the problem is in your faucet. Figure out the brand/model and you can get a repair kit.

If hot water doesn't flow even when the valve is disconnected from the faucet, then you have a problem with the valve or plumbing.

My guess is, unless your water lines were actually frozen, the heater is a red herring and the reason you have all hot or all cold is because there's a worn-out washer in your faucet's mixing valve. Possibly a chunk of it has broken and is moving somewhat freely within the valve, blocking one side or the other.