What happened? It looks like you bluffed a station.
Where was your flaw? You bet the river.
What is the max he can call on the river? Depends. Did he have a K? Is he calling down with any piece of the board, even 2x, even A-high? Without reads, there's no way of knowing what bet size you need before he'll fold. And if he's a true station, then there's no bet size large enough.
Unless you know your opponent can lay down a hand, you shouldn't be bluffing.
Once he calls your c-bet, you're done unless you improve.
The less you bluff at these stakes, the better you'll do.