I'd like to haul out three Scriptures to show you where I'm coming from:
Your interpretations of which are called into question by your admission that the apostles taught orally at least to start.
So you and I agree that the Church carried such authority at least at one time. So that raises the question of if/when that authority was rescinded. I suppose we could also ask why that authority, once granted, would be taken away.
The Catechism assumes that the Bible and Tradition will always harmonize. But they differ considerably about how we're saved. Hebrews, for example, says Christ sacrificed himself once for all time, whereas the RCC says our salvation is dispensed little by little, Mass by Mass.
Whaaa??
This is what I find alarming about all the differences and additions. We're supposed to venerate & pray to beings other than God
Only certain people.
I would add that there is a very salient difference between "veneration" and "worship". Veneration of saints is permissible. Recommend, even. Worship, on the other hand, is for God and nobody else.
we're supposed to believe you have to suffer in Purgatory despite Christ's sacrifice
Purgatory is the cleansing of one's personal attachment to earthly desires. For some reason, this gets interpreted (by Protestants) as some kind of substitution for or replacement of Our Lord's sacrifice.
It is in fact the completion of His sacrifice. It is the process whereby this mortal puts on immortality. Nothing impure can enter Heaven. As sinners, we are impure. So in order to enter Heaven, somehow we must become purified. If we're bound for Heaven and we're impure in life, we must be made pure after death.
Frequently Purgatory is referred to as a place and I sometimes don't think that's very helpful. 1 Corinthians 3 describes a process as much as anything and that, I think, is a better way to phrase it.
I sometimes think that if Purgatory had been called
Purgation, the intent might have been clearer.
that you can do certain works to reduce your time in Purgatory,
I gather you don't believe in Purgatory so I don't see why this should be a troubling notion for you.
and that a church, council, or man is "Infallible." Well how do I know they're infallible?
Men are fallible. However, the Pope, for example, is understood to be infallible under certain circumstances. When he invokes the teaching authority inherent to his office, he is speaking infallibly. That is, without risk of error. It's not a permanent condition; when Pope Francis burps, he isn't burping infallibly. Even all or most of his public statements aren't necessarily binding upon the faithful.
But when he invokes his teaching authority (which, offhand, I'm not even sure has happened yet during his papacy and I'm too lazy to to check), the faithful are obliged to listen and obey.
How do you know about this whole infallibility business? Well, Our Lord said that He would be with us always, even unto the end of the age. He also said that He would send the Comforter, the Counselor, the Holy Spirit to us. Thus it seems unlikely that He would allow the Church to fall into error. So there must be a guarantor of truth to guide the faithful. As wonderful as Sacred Scripture is, it does not discuss every possible subject. It is static and unchanging. It is perfect in what it says... but it doesn't say everything. Sacred Scripture may be silent on important issues so there must be some sort of guide for when new challenges arise in life, as they tend to do.
Further, even Protestants mostly agree that Sacred Scripture must be interpreted. All they really disagree on is who should do the interpreting. If the meaning of all sections of Sacred Scripture were self-evident, surely we would all be united as one body. But obviously we're not.
It follows that the Church is also guided in her interpretation of Sacred Scripture so that the meaning and truth of it are faithfully conveyed. In order for that to be possible, the Church must be protected from error in her understanding of the scriptures.