How are you so sure?
Like the 10 commandments? Each and every “rule” is a true demand of authentic love. Simple as that.
A mortal sin is a rejection of God. So, sounds like good advice to me to avoid it. Most people overlook the 3 conditions necessary for a sin to be mortal, which very well likely reduces most materially grave actions to venial sin. A negative feeling of guilt that is not alleviated by hope is perhaps scrupulous and likely the result of an incomplete understanding of the Catholic teaching of God’s loving mercy.
Nor did many of the disciples. See John 6. Conversely, I know many converts who returned to the Church precisely for the real presence.
See my third point above. A kind of doubt is not the same as a flat out rejection.
I cannot imagine being anything else.
“Lord, to whom shall we go? You have the words of eternal life; 69 and we have believed, and have come to know, that you are the Holy One of God.”
Be not afraid to wrestle with these and more questions about the Catholic faith. Don’t throw in the towel just yet.