The only Conservative government that has ever changed or repealed any firearms legislation was Harper ending the long gun registry. Otherwise, there have been none.
"...If the Firearms Act is repealed, the provinces will..." Nope. Firearms legislation is strictly Federal as it's in the CC of C. The Provinces cannot change Federal law. Mind you, Trudeau the Elder's constitution lets 'em ignore any Federal law they don't like and ignore anything the SC of C decides.
In any case, the biggest issue with the FA is that it's based on French Common Law, not English and the number of clearly blatant Charter of Rights violations in it.
It's also far more important that the property rights deliberately left out of Trudeau the Elder's constitution are written into the Constitution.
"...to protect life..." In the late 80's, that was the first reason one could have for owning a restricted firearm. Not that you'd ever have gotten the permit giving that reason.
"...destroys his retirement investment..." Firearms are a lousy investment. Very few, other than milsurps, ever increase enough in value to even be considered an investment.