Feeney was a quite useful priest so long as he kept to his mission given him by Richard Cardinal Cushing of establishing St. Benedict House at Harvard and to use Feeney's considerable intellect in a direct assault on communist ideology at Harvard. He then took off on his own tack and started the heretical view that unless you are a practicing and properly baptized Roman Catholic, you will go to hell. In one book shown to me by a Feeneyite client, he also degenerated into Donatism by suggesting that readers be baptized often because you never know whether your previous baptism(s) were marked by the correct intention.
The notion that he did not repent and repudiate his heresy is the understandable lie of those who insisted on continuing his prior heresy and simply denied that he had repudiated the heresy. That they say so does not make it so just like the claims of SSPX that they are not REALLY sedevacantist or not REALLY anti-papal or not REALLY schismatic or not REALLY operating on their own personal interpretation of Tradition (YOPIOT AND TOPIOT) does not prove that they are right as to any of those things or not REALLY what they are.
Your YOPIOT theory as to the meaning of extra ecclesia nulla salus is like some socially insecure boys who just cannot enjoy the tree house if girls are allowed in. There is a certain poverty of spirit in the notion of the Feeneyites that EENS means that they are an ever more exclusive club of the elect with ever more of those who take umbrage at the grabbing of their lapels by hysterics heading straight to hell. Ironically, the Feeneyites put themselves into an impossible intellectual contortion whereby they would effectively condemn themselves to hell but for the happy fact that their heresy, like all heresies, is wrong. See the regular schismatic whining about: Why can't the pope be as mean to the heterodox as he is to "St." Marcel, the Excommunicatus?
If Feeneyites or SSPX, for that matter, REALLY believe their deviations from Catholicism and Truth, via the route of invincible ignorance and despite superficial appearances of sophistication, any of them may yet be saved. In the case of Feeneyites, that would be in spite of themselves.
Outside the Church there is no salvation.
This is a defined dogma. It can never be changed or denied. You have called it a heresy. Wise up.