I get my stuff about said creed from the New Advent site. They break down the putrid doctrines from the bowels of Hell into layman's terms....
Whosoever will be saved, before all things it is necessary that he hold the Catholic Faith. Which Faith except everyone do keep whole and undefiled, without doubt he shall perish everlastingly.....
There are too many fun things to do today to argue, but this is worded funny. The tenents you posted are not the limits of what the church teaches, if they were, there would be no problem. The church claims authority over all christians, which is where the problems begin.
And yes, Athanasius may have not written it, but it does bear his name.
And this from the catechism....
818 "However, one cannot charge with the sin of the separation those who at present are born into these communities [that resulted from such separation] and in them are brought up in the faith of Christ, and the Catholic Church accepts them with respect and affection as brothers .... All who have been justified by faith in Baptism are incorporated into Christ; they therefore have a right to be called Christians, and with good reason are accepted as brothers in the Lord by the children of the Catholic Church."[272]
Doesn't say anything about those who leave the church.
845 To reunite all his children, scattered and led astray by sin, the Father willed to call the whole of humanity together into his Son's Church. The Church is the place where humanity must rediscover its unity and salvation. The Church is "the world reconciled." She is that bark which "in the full sail of the Lord's cross, by the breath of the Holy Spirit, navigates safely in this world." According to another image dear to the Church Fathers, she is prefigured by Noah's ark, which alone saves from the flood.[334]
846 How are we to understand this affirmation, often repeated by the Church Fathers?[335] Re-formulated positively, it means that all salvation comes from Christ the Head through the Church which is his Body:
Basing itself on Scripture and Tradition, the Council teaches that the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and Baptism, and thereby affirmed at the same time the necessity of the Church which men enter through Baptism as through a door. Hence they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it.[336]
Case closed. Have a great weekend.