As for your first point, I don't really see an issue here. The URLs in the operations metadata should point to the right WPS endpoint. As it is not always in your power to correct this, some kind of override mechanism would be thinkable to strictly use the URL used in the connect-method. Feel free to make a feature-request for this.
As for the second point, you are probably right, the "all" identifier could be used here. It would be great, if you could create an issue with a possible solution attached.