HiCustomer welcome to justanswer. My name is IKE.
The TDC sensor is inside the distributor, and determines the ignition timing at start-up and when crank angle is abnormal. Without doing the actual testing of the sensor, it is impossible to say for sure, but this code usually indicates a bad distributor.
That explains the extended cranking at times. It hasn't completely failed yet, but it is on the way out. If you can afford it, I would recommend getting a Honda distributor and not aftermarket.
The only places I might suggest are E-bay or a salvage yard. Salvage yard will at least allow you to exchange the part if it is bad.
Ebay is okay if you can find a seller with a good feedback score, and make sure you let them know you want a genuine Honda part.