How do you explain the quotes?

He was indignant and scandalized by Assisi, and became convinced of the need for bishops, yes.

He called the pope an antichrist, yes. But not an antipope.

“We May be obliged to believe some day...” does not mean he believed it in the present (and his recent past would suggest the opposite).

He called the pope an antichrist, yes. But not an antipope.

So it's possible for an antichrist to legitimately be the Vicar of Christ?

+Lefebvre was clearly open to sedevacantism, did not condemn it, and felt that it indeed might be the case that the V2 papal claimants are/were not legitimate popes.

No.

He was closed to it, but open to the possibility that the Church might some day declare it.

Until then, it was not possible.

I more mean the one where he said "I do not say you cannot say this Pope is not Pope..."

I have no explanation for that one.

I could offer one, but it would be guessing.

This is the classic reponse.  This is the "Resistance" line.  This is vintage Williamsonism.  We wait interminably until another future pope, or some kind of specially appointed conclave, or whatever, makes the call.  Meanwhile, we poor saps in the Catholic laity, (and priesthood) simply tolerate the enormities of the reigning pope.  We either like it or lump it.
I think it's all baloney.  We know exactly what and who these "popes" are.  They've behaved intolerably in our faces for almost fifty years.  I, for one, have had enough.  Let the sedevacantist banners fly. I'm not waiting for a phony church to declare anything about anything.

You have just admitted impatience (ie., inability or refusal to suffer) led you to your new position.

No.

He was closed to it, but open to the possibility that the Church might some day declare it.

Until then, it was not possible.

False.

It is possible we may be obliged to believe this pope is not pope. For twenty years Mgr de Castro Mayer and I preferred to wait…I think we are waiting for the famous meeting in Assisi, if God allows it.” (Talk, March 30 and April 18, 1986, published in The Angelus, July 1986)

For anyone who wants to know the truth of what +Lefebvre thought about sedevacantism without the Johnson spin --
http://www.fathercekada.com/2012/09/04/pro-sedevacantism-quotes-from-abp-lefebvre/

Right.  Even Johnson could not find a way to explain this one away.  This means that, oops, +Lefebvre considered it a tenable opinion.  Unlike you, he did not consider someone who held the position to be schismatic and/or heretical.

Oh, I can definitely find a way:

An out of character remark does not suffice to overturn an entire string of comments and actions to the contrary.

I only hesitate making the observation because some will use it to attribute to Archbishop Lefebvre a general inconsistency (as some sedes do).

+Lefebvre himself admitted in one of Davies' books that he was sometimes excessively (but justifiably) indignant, and what was said in such moments could certainly not stand as a principle (especially when, as noted, such comments tended to run contrary to an entire 99%-linear line of action opposing sedevacantism).

I think his position was so overwhelmingly opposed to sedevacantism that to attribute inconstancy to him would be unjust.

But that doesn't stop his opponents from turning the exception into the rule, and running with it (as you are doing).

An out of character remark does not suffice to overturn an entire string of comments and actions to the contrary.

This was not by any means out of character --
http://www.fathercekada.com/2012/09/04/pro-sedevacantism-quotes-from-abp-lefebvre/

You will not find a single condemnation of sedevacantism IN PRINCIPLE from the Archbishop.

You keep citing The Nine, but The Nine situation was not primarily about sedevacantism.  At the time of the split, not all of The Nine were actually sedevacantists.  They were more upset about the toleration of Novus-Ordo-annulled couples at their chapels and one particular priest who was serving with the SSPX who had not been conditionally ordained ... because he refused ... and about being required to offer the John XXIII 1962 revised Tridentine Missal.

Now, SOME of The Nine were in fact sedevacantists, and +Lefebvre just wanted them to keep it to themselves.

Then The Nine really acted inappropriately, and this embittered the Archbishop against them.  This was in 1983.  But by 1986, on the eve of Assisi, the Archbishop was still on the verge of coming out openly as sedevacantist.  In fact, he implied strongly that both he and Bishop de Castro Mayer were privately sedevacantist ... but were waiting to come out openly with it.  Those who knew Bishop de Castro Mayer say that he was in fact privately a sedevacantist.