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There's no obligation to avoid priests who are allegedly "compromising on doctrine".  That's between them and God, at the end of the day.  None are required to effectively punish themselves on account of the priest, or, worse, punish their families, with deprivation of Sacraments on account of a compromising priest.

Would you apply this to the non una cuм issue?

It would be protestantism, only if these things were decided by the Church. Unfortunately we only have guesses how to behave not a definitive ruling from the Church.

Exactly.  Sedevacantism is a "guess".  So is R&R.  None of us knows how to live in these times with CERTAINTY.  The only thing that is certain, is to be a Trad and avoid V2/new mass.  For that, we have doctrines and councils to follow.

Just to be clear, sedevacantism is an opinion.  You just admitted it.  Then, in your quote below, you contradict this and elevate the idea to something more.  That's the flaw.  R&R does the same thing.

There is something fundamentally wrong with saying Pope Leo is the Pope of the Catholic Church, but not following anything he says.

This is full of generalizations. 
1) There is also something fundamentally wrong with there being no pope for 60 years.  Heretic pope or no pope...Neither situation is "normal".
2) "Not following anything he says" implies that he's given orders which are direct, clear and with spiritual penalties.  That's debatable.  No V2 official has ever said, written or given a formal speech which said that catholics who reject V2/new mass are guilty of sin or are schismatic.  It's all optional.  There is no spiritual penalty for ignoring it all.
3)  Even sedes reject the new Holy Week, which Pius XII created.  He was a true pope and sedes don't follow him on that order. 

The only thing I am protesting is Pope Leo and I attend Masses the Saints would recognize, so how can that be Protestantism?

Naming Pope Leo in the mass doesn't change the mass' intention, nor make it unable for saints to recognize.  There are multiple liturgical experts who have explained (prior to V2) that the "una cuм" is NOT what sedes (i.e. Fr Cekada) said it means. 

Again, in history, there were MULTIPLE times were 2 or 3 popes claimed to be the true pope.  The 'una cuм' debate raged then.  There were saints ON BOTH SIDES of the debate.

Based on history and based on liturgical experts...it is categorically WRONG to claim that the 'una cuм' is a moral issue.  Anyone who makes this argument is uneducated or agenda-driven and guilty of many deceptions.