Archbishop Lefebvre was not some kind of super bishop whose decisions put an end to all discussions.
No one is making +ABL into a super bishop, after all, all he did was what the Church has always done, and the SSPX is still doing that.
If the new consecration rite was used, that is enough for positive doubt. There is no need for any other investigation.
Not according to what Trent's catechism teaches. This point of contention is in fact contrary to what it teaches.
We think it's x, you think it's y.
More accurate to say, "We think it's x, the Church teaches y."
By 2123 or so we will all be dead, and then we will know the answer.
Unless, of course, we get a real Catholic Pope before we die.
True ha ha