"Seems to enter at PP I have to enter a lottery for BWCA. There must be someone I can talk to."

I don't think you have to get a Moose Lake permit that way - you would just do a self-serve? Day-use permit since you wouldn't be camping in BWCA that first day - unless you were using a "tow" in which case, the outfitters permit would cover your trip to PP on Day 1

Its been years (1996 or so?) since I've used Prairie Portage entry via Moose Lake, so I'm not an expert, but I think that's the way you would do it.  As to the BWCA permit for the return - I'd just see what is avaiable for the day you plan on crossing back to US side - or find a day with an open permit and pick that one to enter with - maybe it is just that "Entering form Canada" and I don't think they limit those? 

You really ought to call a BWCA Ranger Station and talk to them about it - or an outfitter, I suppose.  At least there is an advantage to camping the latter half of the trip in US - no fee other than the one time $15 as compared to $21.50 a day for the Quetico.

And I sorta doubt that IC's method is technically legal - as I seem to recall, once you leave BWCA for Quetico (or just a return to Ely for a day), you'd need a second/new BWCA permit to re-enter BWCA - can't go in and out as you please ?  but again, talk to the Forest Service people about it - the reservation people are likely just contractors or a concession I think, and may  or may not give you the correct answer