How would you want the Protestant people to refer to our clergy? 

I’ve met Protestant ministers at town gatherings (festivals, and such). I always just say “hello, Mr. (insert name here)”. Never by Pastor....

I'm fine with "pastor" as its really not a term we use and it really doesn't mean much.  It just means that he's the main guy at a Protestant ecclesiastical community/ѕуηαgσgυє of satan (depending on how polemical you feel like being  ) and doesn't seem to give any real ecclesiastical legitimacy.

By contrast, I'd be more uncomfortable with "reverend" as I think that literally means "revered one" and that's not an appropriate title for a heretical preacher (even on the off chance his heresy is only material, I still think its inappropriate.)

I'll use pastor because it's a generic means of addressing the leader of a Protestant church.  Nobody would mistake the title for Catholic.  

Protestants are big into humility, almost to the point of disrespecting their position(as we can see with Prot-influenced "Catholics" like Bergoglio), so I doubt they'd mind or put up a fuss about referring to them as Mr.

I don't know if this is a new thing, but I've heard that referring to Popes by their name (ie. Bergoglio) is common in other countries, but not so much in the US.

(I realize you're likely calling him that 'cause you think he's an antipope, but I think in some other places people just do it.

I wouldn't know. I'm almost certain you use the regnal name(is that the right term?) in all English-speaking countries. For the others I'm not sure. I've seen people from many other European countries refer to the Popes online and also only use the regnal name, but they were all speaking English so maybe they might use the Popes' Christian names in their own languages when speaking colloquially. I don't know. I'd always regard it as disrespectful, but the man himself has asked people to call him Jorge which is even less formal than Bergoglio, so I've always tended to call him that even though I'd refer to his predecessor as Benedict(despite myself having had the same doubts over his status as a Pope too).

I'm definitely in the "We have to function as though he's pope unless or until there's a church ruling to the contrary" camp, so I still refer to him as Pope Francis.  Though I'll admit I have a harder time calling Francis a Catholic with a straight face than some of the others (not that I think JPII or Benedict were particularly great, but Francis seems much more likely to overtly not believe in Catholicism, whereas some of the others more just seemed to use really gross and previously condemned tactics to try to promote Catholicism, like ecuмenical interfaith gatherings.)

But yeah, to somehow tie this to the topic of the thread, I can see why Sedevacantists wouldn't want to call a conciliar Pope "Pope" because that gives them theological legitimacy.  I don't see a similar problem with calling a Protestant pastor "pastor" and I don't think in most contexts that would necessarily indicate either that we see them as truly ordained, having received the sacrament of holy orders, or that they're part of the true religion.  I grant that "reverend" is a bit closer to doing so, since technically it means "revered one" and I'd be uncomfortable calling a Protestant pastor "reverend" for that reason