Those are all the questions that would go into the Negotiations, OTL they took 5 years to reach agreement on them.
I gave thought to having it take another couple years, but that would have butterflies for the NW ordinance,
Labrador would be part of Quebec's Northern Claims. ?The AoC US agreed to support Quebec in them, would the 1789 US do the Same?
Okay your going to have to be quite succinct in what you mean by northern claims when your referring to Quebec. What you are currently suggesting does not make any sense at all...
Along with the Quebec act which extended the borders of Quebec to include the valley of the Ohio and the entire St. Lawrence Grt Lakes basin. Administration of the Coast of Labrador was also redistributed. The southern
shore (North shore of the G. of St.Lawrence) and the islands of same Gulf were transferred from the Fishing post of Newfoundland to Quebec as well but the entire northern coast of Labrador was reaffirmed as remaining in the jurisdiction of Newfoundland. If Newfoundland remains a Br. possession then so does that coast. As to the rest of the northern claims. They do not extend beyond the height of land separating the Grt. Lakes and St. Lawrence from Hudson's Bay.
those lands to the North..are Rupert's land a territory controlled and administered by the HBC. A commercial entity yes but under the protection and operating under charter from the Br. Crown. Its unlikely that a Quebec entity would be able to successfully push any claims in this region against the Br. Crown.
The only effective northern claims of Quebec would be the "Haute Pays". The entirety of what would become OTL Upper Canada (The name is not just made up after all It is the extension of its"Lower French speaking cousins") the State of Ontario that you suggest would not exist. These are the only "northern claims" that the Quebec entity would have that would be of any consequence to them. Anything less and you are offering them a bunch of Rock, stunted forest and tundra. Long before your negotiations ended...all the powers of any influence in Quebec ( Clerics, Seigneurs and yes yankee mercantile interests) would probably invite the Brits back to keep the Americans out of the rightful backyard of Montreal. If not the Brits they would certainly argue for a stronger French presence... Afterall if this is what they get from rebelling against the Brits in favour of "les Americains" ( to whom they have no affinity to begin with and indeed a long history of hostility where New England is concerned, ....need I say more) Well that s the reason they didn't rebel in the first place remember... ( guarantees of Religion language and an Economic hinterland for the merchant class of Montreal)..Obviously such a disposition that you suggest would leave a very "Sour" taste indeed among the Quebecois regarding "les Americains"..
As to form of gov't. Republic perhaps but a very conservative one at that. There are still less than 200,000 Quebecois at this point ( and it of all the possessions of the Brits in North America still has the feel of the Ancien Regime to it). France would want to receive it back if they could as a prid pro quo for their support of the American rebellion. They are going to want something to show for there efforts after all. Thats not likely to be on of course but a Cadet branch of the Bourbon's may be likely in some kind of Arm's length fashion. Say a Grand Duchy under Louis-Stanislas or Charles-Phillippe ( and not in direct line of succession to the Crown of France except through exceptional circumstances). Informal but separate links to the Crown of France and within the Economic hinterland of New England but with commercial interest for the French as well.
Any Quebecois regime would immediately lift the ban on settling west of Montreal of course in the same way that the Americans are moving into the Ohio, the Quebecois would begin settling in the Upper St. Lawrence and Grt. lakes. South Ontario in that respect is prime real estate for them. Given their historically good relations with the natives..this should go reasonably as smoothly as in OTL as the spread west would probably be more gradual unlike the rapid settlement of loyalists in the region OTL.. I'd be surprised actually if the Quebecois and natives of the region did not assimilate to each other to avoid being swamped by the Americans.
If the Revolution in France still goes off Quebec would be a bastion of royalist support...If Louis -Stanislas or Charles are in Quebec though.. they will not be in France agitating for counter revolution. The flames that gave birth to the more radical elements of the revolution may not be present and France may just make the transition to Constitutional monarchy. In which case the destruction of the revolutionary and Napoleonic Wars will be avoided, along with all the blood shed. There will be a huge surplus of French speaking Catholics and Catholics from across Europe to to settle in Quebec and Latin America (New Spain, Rio de La Plata, New Granada and Peru) as well as Brazil.
Of course with France transitioning to C.M. There is the whole matter of Poland-Lithuania and its final partition to blow things into the dumper if you will. But I think things are a little too far gone by the 1790's.