Frog care: finding a vet, safe tank rocks, and normal leg spasms?

Thanks for your question - to find a veterinarian in your area, you can check the AAFV or ARAV websites. Additionally, UC Davis is a couple of hours from you, and they have a department at their veterinary school that will see both fish and frogs.
For the rock size - you are correct - you want to have larger rocks so that your frog doesn’t accidentally ingest any of them.
For your last question about the spasms - without further description I would be unable to determine if this was normal or not, but I would recommend ensuring that you have a complete and balanced diet for the species of frog that you have. Nutritional deficiencies can be very common in frogs, and can result in “spasms” in them.
I hope that helps to answer your questions, and good luck!