I think that Mulroney might find it easier to achieve most of his policies starting in 1979 rather than in 1984. For one thing His economic policies are largely responsible for helping Canada lift itself out of the economic mess that Trudeau left us in. His policies were continued and expanded under the Chretien government to great success and in terms of economic policy he's probably the single most underrated PM in Canadian history (This article makes a great case for that claim
http://policyoptions.irpp.org/magaz...trudeau-leaves-a-legacy-of-deficits-and-debt/). Plus in 1979, the debt wasn't as out of hand as it was in 1984 when he took office in the OTL. the Lions share of debt incurred by the Chretien and Mulroney governments between 1984-1995 was because of the debt transfer payments on the massive Trudeau debt. Even with Mulroney's first budget, his government increased revenues and reduced expenditure, but still ran a record deficit because of the debt payments. Mulroney also ran operational surpluses continuously from 1987-1993, but the debt payments were still too big (not to mention the early 90s recession hitting the Canadian economy at the same time, which also attributed to the debt). Canada wasn't able to pay down its mountain of debt until the 1995 budget cuts under the Chretien government, which finally allowed Canada to put its books in order. the Mulroney government was unable to do these cuts while they were in power mainly because of the backlash that the austerity would cause (regardless of its long term benefits). the Liberals in comparison were in an ideal position to get away with it due to the opposition being in shatters and there being no real threat to the Liberals losing in 1997 or 2000.
In 1979 however, Canada was in a slightly better economic position than it was in 1984 with a smaller level of government spending to contend with. Putting all of this into account and without having to deal with the wreckage left behind after the NEP or the gigantic debt accumulation of the Trudeau government from 1980-1984, Mulroney would likely be able to accomplish much more and leave Canada in a stronger economic position during the 80s and 90s, with a smaller federal debt, more growth and some possible surpluses (depending on how much more sustainable the debt transfer payments were to deal with in 1979). If Mulroney doesn't have to continuously borrow to finance the debt, then he's going to run successive surpluses at least until the early 90s recession hits.
In terms of the Quebec Referendum. In The Original Timeline, The no side won by a large margin (almost 20%) It's unlikely that there'd be any chance of The Yes side winning that Referendum to the point of verging on to the absurd. So i think that
fjihr's suggestions about the referendum are logically unfounded.