was this ruling incorrect

Yes. The decision is fundamentally flawed and if the US survives this, it will be discussed in law reviews for decades to come.

If so, how do you square that with the majority of justices ruling that way

Are you presuming that a reactionary majority in SCOTUS ruling something squares with "correct"? Setting that aside for a second, I'll answer it by saying their decision makes it legal for the president to commit crimes in an official capacity, and that decision is wholesale incorrect by virtually any standard other than "Conservative Party go Brrrrr". Say that out loud a few times: "it's legal for the President to commit crimes in an official capacity". This is defacto opening to kingship / authoritarianism. If you go read the entire constitution (it's pretty short) and you'll recognize that these same 6 jurists cannot back this decision up with anything remotely resembling what the constitution says. It goes against all of the language holding our government officials accountable to the law. So yes... I square it quite easily by saying that all 6 of the majority decision jurists are wrong and just because it's a majority doesn't make them right.

Or do you as a fellow armchair ianal basement dweller get special privileges when it comes to your legal opinions vs that if scotus judges?

This argument doesn't go as hard as you think. My whole point centered around the fact that you shouldn't pay attention to me, but that you should pay attention to the dissent WITHIN THE SUPREME COURT itself. My opinion here truly doesn't matter (which I suppose negates my first to responses above, but you asked...) but Sotomayor's legal opinion surely matters. That was my point.

All I’m saying is that if I’m POTUS and I’m considering a questionable “official act” i know who I’m going to to clear it first.

The SC put it on the lower courts, which means any challenge to "what's an official act" will just come back to the SC upon appeal. The conservative majority can choose to hear or not and if they do, hear any challenge, they can rule along party lines in favor. Sotomayor is saying, rightly, that other than a mild delay, this is effectively a rubber stamp for the President to commit any crime while in office. Further, my argument is that if Trump gains office again, he won't bother clearing anything - he'll go straight into persecuting anyone he deems disloyal. He's already saying Kinzinger and Biden and Liz Cheney should meet a military tribunal (though there is absolutely zero jurisdiction). In any authoritarian country, this means at least life imprisonment if it doesn't mean a firing squad. And he can do it and THEN see what the SC says. He's not going to clear anything because he knows they are in his pocket, and he can use their own decision to eliminate them if they don't play ball on ruling what is official or not. The SC may think they have power right now, but take this forward a year from "First day dictator Donny" and tell me the Supreme Court can do shit? They've created their own monster.