[Babalatexi]

I think you played it well. I'd bet slightly more on the flop as it's 3-way so you get a call more often than HU but that's just a minor detail or perhaps a matter of preference. You can't really bet/fold the river since the stacks-to-pot-ratio is so big already you'd be forced to call a push. The "good" think about the river is that villain's range is extremely polarized: he either has 7x, (( very, very, very unlikely 34)) or air. A passive and bad player like this is almost NEVER over-betting an 8, 2pair or even set on this river. Because there's about no draw he could have on the flop that didn't hit on the river (no missed FD's), there's not really much he could be bluffing with. Hence, a fold becomes very easy.

Edit: spelling