Be very, very careful of stating that...other than the original teachings of the Catholic church, as far as I know, only the Immaculate Conception and the Assumption have been declared as Infallible teachings.
No, those are examples of the Extraordinary Magisterium. That is not the only teaching that is infallible. There is also the Ordinary Universal Magisterium. I am amazed how this error permeates most Catholics’ thinking.
By this thinking you are suggesting that every other teaching in matters of faith and morals for the last 2,000 years is not infallible.