Evenin’ brother! When a catholic tells you ‘you cannot know your salvation is secure’, ask them which Promise from God has ever failed?
Well, I can only speak about my own experience. When I was a Catholic, sometime in the last century, I didn't know God promised complete assurance of salvation to mankind. Now that I have true faith, I understand it perfectly. Being as I am concerned primarily with Heaven/Hell, I will leave others to discuss the finer points of other less important doctrines. Notice I did not say unimportant doctrines, just less important, when compared to Heaven/Hell. Later bro.