Based on the following, can I at all call myself a Christian? Only serious answers please, since this is something that means a great deal to me and bothers my mind constantly.
No, you can't, at least with any degree of honesty. As a Catholic, you must have confessed the Apostle's and Nicene Creeds. To be a Christian, you have to
believe the stuff you confessed in those creeds. You have to actually
believe in God, the Father Almighty, Maker of Heaven and Earth, and in Jesus Christ, His only Son, our lord, Who was conceived by the Holy Ghost, born of the Virgin Mary, suffered under Pontius Pilate, was crucified, died, and was buried, Who descended into hell, and on the 3rd day rose again from the dead.
You know the rest, or should. The point is, that those are the things that Christians believe, and that make us what we are. It's not about being nice or thinking that Jesus was probably a swell guy. It's about what you believe to be the
truth. You have to look at those confessions and say, at least inwardly, "Yep, those are the facts. Water is wet, 2+2=4, the sun rises in the east, water boils at 100 centigrade and freezes at 32 Fahrenheit, God created the Heavens and the earth, and Jesus Christ rose from the dead, ascended into Heaven, and will come again to judge the living and the dead."
That's what Christians believe, and if you don't, then you aren't one, however many other wonderful things you may be. You may be a genius and a humanitarian, you may be beloved of all and a defender of the downtrodden, and the grateful multitudes may lift their hands in blessing as you pass. But if you don't believe what Christians believe, then you aren't a Christian. It's really as simple as that.