Tom:
Good to hear the water pump and T-belt is fairly new.
However, when was the coolant system last purged? Could also be a bad thermostat causing some grief, as well as like some have mentioned regarding hard water.
As far as the amount of loss from the reservoir, it seems somewhat normal to me.
Also, a bad radiator would cause "smells of coolant" to happen at times. At least that was my experience awhile back with an older 944n/a I worked on. In that case, it turns out the thermostat needed replacement and so did the radiator.
Hope this helps and good luck with that. At least now you know where the smell was originating from.
