then all Protestants who have given their lives to Jesus are part of the Catholic Church, correct?
No, not correct. If someone gives his life to Jesus, he would probably be a brother in a Catholic monastery or a priest. He certainly would not be busy protesting His Church.
You must accept the Catholic Church as supreme or you will not be saved.
As One Holy Catholic and Apostolic, as per the Nicene Creed. Correct, that is necessary for salvation. However, that does not contradict that we don't know who is not saved (*), because we don't know if they enter the Catholic Church at the hour of their death, if not sooner. It is our most fervent prayer that they all do: "Holy Mary, Mother of God, pray for us (me and you) sinners now and at the hour of our death"; "O Lord Jesus, save us (me and you) from the fires of Hell, bring all souls to heaven, especially those (you) who is in most need of Thy mercy".
controlling who is a Catholic
The Church controls who is visibly Catholic, that is, who is visibly partaking of her sacraments. The Chruch does not and cannot control who is internally Catholic, that is, has a desire to be Catholic but is prevented from it by some circumstances.
And most Catholics refuse to honestly admit this position, trying to shade it in ecumenical terms
Most Catholics are themselves confused by the false ecumenism that infected the Church following the Second Vatican Council. But you must agree that it is not an easy to grasp doctrine even if it were taught properly. I don't think very many Catholics are trying to deceive you on purpose. I sure don't.
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(*) We do know that the canonized saints are saved, but we don't know who is saved outrside of that small circle of people, and who is not saved we never know for sure. We don't have a list of reprobates in the same sense as we have a list of canonized saints.
Does 841 - in context and in whole - not state that Muslims will be in Heaven with you, because they are followers of God?
As One Holy Catholic and Apostolic, as per the Nicene Creed.
Catholic meaning universal Church, not that headed by the Pope in Rome? Meaning Protestants and Orthodox would be part of that same Church?
But you must agree that it is not an easy to grasp doctrine even if it were taught properly.
It is confusing because it is a dogma of man, not of God. It really is simple: if you really claim that only Jesus can offer salvation and know a man's heart, then state as much. Open up the Communion to all who wish to partake. It is between the man and Jesus, not the Church and man.
My own denomination - Free Methodist - practices open communion. Anyone who wishes can partake. It is not our role or ability to control who can participate in the sacrament. It is between God and the person.
Additionally, we do not condemn a man to the fires of Hell (which MarkBsnr clearly showed is one of the rites of the Catholic Church); if someone is causing strife or acting in what we believe is direct contradiction to the teachings of the Bible and refuses to repent, we ask him to leave the Church, but do not "yank his Heaven pass" like ex-communication.
He's asked to go worship elsewhere for the betterment of the local congregation and for his own spiritual health. But we do not state he is lost; that is for God and God alone.
But then, if this policy of open communion and "we do not decide who is and isn't saved" was truly followed, then the control is no longer left in Rome, so surely the early Church could not allow that! So the Catechism was created to dictate and maintain control over the masses.
And over time, as the Church became the accepted "gate to Heaven", and the dogma of infallibility was strengthened, the Church finds itself having to defend the indefensible, so twisting itself to let in Christian-slaying Mohammed but denying Christ-loving Arne.
The need for control by the early and middle aged Catholic Church became the justification for restriction, even if not Biblical, even if confusing and misleading to those truly seeking Christ. Men used the Church for their own betterment, and the Church never corrected for that.
I don't think very many Catholics are trying to deceive you on purpose. I sure don't.
You are most assuredly correct; however, the teachings of the Catholic Church, and its placing itself as the arbiter of salvation (one that is infallible at that) is the font of all misunderstanding related to salvation.
If the rank-and-file Catholics are confused, there is no other place to lay blame but at the foot of Rome. The problem is how do you correct clearly non-Biblical teachings when those teachings have been deemed inerrant?
The Church's desire to be inerrant and infallible is its own greatest stumbling block; they are the twin sins of pride and jealousy. Pride because it cannot admit its own mistakes (take for example the continued refusal to outright admit the sins of the past) and inherent fallibility, and jealousy because it seeks to be the object of worship and salvation rather than God.