^Literally what I've been saying
I know you keep saying the same thing and posting beautiful Catholic and dogmatic teachings over and over, why keep quoting the same thing that there is no argument over?
Certainly heretics who have never been Catholic are outside of the Church, and all who die heretics regardless of whether they were Catholic or not will go to hell forever - that is not in dispute, never has been, never will be - this is what Florence is teaching and is in harmony with all of your other excellent quotes (except the ones I noted that are misquoted by MHFM).
Look, you said that you agree that Catholics, most notably popes, who've fallen into the sin of heresy can be absolved through the sacrament of penance. If you actually believe this truth, then you understand that the Church only permits the use of this sacrament to those who are members of the Church. Hence, Catholics who've fallen into the sin of heresy must be members of the Church who've fallen into the sin of heresy. It's really not complicated.
Heresy is a mortal sin, Catholics who've fallen into this mortal sin have got to get to the sacrament of confession asap - but the nature of this particular sin makes that more unlikely than with other mortal sins. So it's not that the Church has kicked them out, She hasn't, it's that they want nothing to do with her anymore - THAT is the nature of the sins of heresy, apostacy and schism, this is what PPXII is teaching in MC.
The sede narrative hinges on the error that Catholics who've fallen into the sin of heresy are banished from the Church, insisting that these heretics are not members of the Church - I keep saying if they were Catholic, then yes, they are indeed members of the Church who have fallen into the mortal sin of heresy and that it is the Church herself who urges them to get to confession and repent - which she only does to members of the Church.