Is it safe and/or sustainable to lose more than 2lbs per week?

Yes, absolutely.  We have known people lose upwards of 7lbs almost overnight, simply by cutting out foods they’re intolerant to (typically wheat and dairy).

If we’re talking specifically about two pounds of actual fat, then this is probably not far off the mark – depending on your starting point.  But weight fluctuations on the scales can occur without any change in body fat.  Muscle mass, bone density, hydration, toxicity, menstrual cycle and so forth can lead to weight fluctuations.

Despite our obsession with them, the scales alone are not a great indicator of actual fat loss!