Pull dump or non exhaust elbo

[crofrog]

Are pull dumps considered a potential failure point?

Yes they can and do fail. More importantly when they fail it is very hard to keep gas in the wing. When the kidney dump fails assuming a slightly head position allows you to keep gas in the wing.

If so, how do you exhaust - lower dump or power inflator dump

95% of the time it's using the kidney dump. The only time I don't is when trying to get every last ounce of gas out of the wing, or at the surface starting my descent about 1/2 the time.

- and where do you normally keep your left hand during a dive?

out in front of me, holding a light.