Jim, with regard to your second question, it would not only be presumptuous -- it would also be contrary to Scripture -- to think that we have a guarantee of salvation. That's not to say, however, that we should despair of God's mercy. What we need to be careful of, however, is the error that we can make some kind of profession of faith and be assured we have an iron clad guarantee of going to heaven.
To the contrary, Scripture tells us that our salvation is an ongoing process, not a one time event. If one reads Scripture carefully, we see that we have been saved (Rom. 8:24, Eph. 2:5–8); we're being saved (1 Cor. 1:8, 2 Cor. 2:15, Phil. 2:12); and, we hope to be saved (Rom. 5:9–10, 1 Cor. 3:12–15). Even St. Paul said, "I am working out my salvation in fear and trembling" (Phil. 2:12), "with hopeful confidence in the promises of Christ" (Rom. 5:2, 2 Tim. 2:11–13).
Wow. I can't speak for you, but if St. Paul felt he still needed to work on his salvation, I think it would be foolish of me to presume my salvation is guaranteed!