If +/Fr.J. Pfeiffer was the only priest available to offer you the last Sacraments if you are dying would you allow him to minister them to you?
My answer is, yes, if he were the only priest available, I would allow him to administer the last sacraments to me.
Generally speaking, in our last hours, particularly in these times, we are in no position to turn away a priest, which, whatever else he may or may not be, Fr. P certainly is a priest.
Trent's Session 14, Chapter 7 says:
"Nevertheless, for fear lest any may perish on this account, it has always been very piously observed in the said Church of God, that there be no reservation at the point of death, and that therefore all priests may absolve all penitents whatsoever from every kind of sins and censures whatever: and as, save at that point of death, priests have no power in reserved cases, let this alone be their endeavour, to persuade penitents to repair to superior and lawful judges for the benefit of absolution".It should be noted I think that trads who have been faithful and live according to the true teachings of the Church, attend only the True Mass etc., and have not and will never have anything to do with the NO, really should have no need to worry about God sending a false shepherd to you in your last hour. OTOH, compromisers might have cause for concern.
It should also be noted that we are supposed to pray daily for the grace of final perseverance and the grace of a happy death, and in addition, these days we should pray every day for God to "send me a good holy Roman Catholic priest to give me the Last Rites before I die, and that I receive them with the proper disposition," do this, and surely God will provide for us what we ask.
John 7:8 For every one that asketh, receiveth: and he that seeketh, findeth: and to him that knocketh, it shall be opened.
Haydock: Whatever we ask necessary to salvation with humility, fervour, perseverance, and other due circuмstances, we may be assured God will grant when it is best for us. If we do not obtain what we pray for, we must suppose it is not conducive to our salvation, in comparison of which all else is of little moment.