[benkahuna]

You're suffering from a bout of results-oriented thinking.

You shouldn't slowplay a flopped underfull with a dangerous board (this one qualifies). You got in as a huge favorite. There's nothing more you can do.

If you are consistently finding yourself rethinking this play, you need to take a break from poker and reread the books you've read. None of them even hint that you made a mistake here.

And you did protect your hand by making a pot-sized bet. Going all in w/ really strong hands (but not the nuts) to protect them is a good way to make less money and often only get called by a superior hand. That's bad poker.