I've completed the rival quest, I visited the abandoned hut and saw things there, I rescued Jhod the priest at Thorn Ford, and I cleared out the Erastil temple so that the pond there now heals people. But now what do I do?

Jhod is now non-interactive; I can't even click on him and he's standing still behind some trees at Thorn Ford. My quest journal just says "go tell Jhod when you find the temple" and "find the Stag Lord's fort somehow". Am I missing something or is the main quest now unplayable until it gets patched again?

You're correct. Apparently you have to act in a very specific and strange order to proceed: talk with Jhod at the trading post, and only then does a guy appear at the temple to get rescued, so that you can tell Jhod you found the temple.