With regard to your parents... The Catholic Church also teaches that we cannot judge another's soul. That would include your parents. We can discern, yes, that they were in "mortal sin", but only God can weigh all factors (including their level of knowledge/understanding and/or any mitigating factors). God is also All-Merciful, and if at all possible He would have saved your parents as long as they had not completely rejected him. It is very likely they are in purgatory, and if so, they need your prayers!
On the other hand it is a grave error to say that one's Salvation "is assured". That is the sin of presumption (Catholic teaching) and goes squarely against Scripture on the matter (read St. Paul - he says quite the opposite). We have to "fight the good fight", because at any moment we can fall from God's grace by choosing evil over Him.
But please, trust in God's Mercy and commend your parents souls to Him. It is not Catholic teaching to say they are in hell. You might want to purchase a copy of the Catechism of the Catholic Church to see exactly what is taught on these matters. It's actually quite comforting! ;)
Thank you for writing all that. I'm thinking about what you said.
**On the other hand it is a grave error to say that one's Salvation "is assured". That is the sin of presumption (Catholic teaching)**
Where did you come up with the notion that this was Catholic teaching?
It has been my experience that Protestants, once thinking the have been "saved" or "born again" think they are OK and cannot sin.
Not true for either Catholics or Protestants!