wow some really good questions here, but I don't think you will get answers that mean enough for you unless you start from a different perspective.
you say, 'The message of Christianity is love, plain and simple.' but it isn't so plain or so simple because we don't really know what love is in the first place. Love isn't at all like anything else in the universe: with a shape and a clarity (although at a much deeper level it does have both). Love isn't something we start by 'knowing' at all. We all have an idea about what it is (mostly from our experiences at home and with special friends) and, as we go through life, we find that what we thought was love turns out not to be so lasting after all and so the search goes on and more and more illusions shatter. The worst times come when we realise that we are not the good persons that we thought we were. It is only at this point - when our own efforts start collapsing around us - that we begin to realise (provided we can still hear through all the noise) our intrinsic and overwhelming need for God. It is trite to say that 'God is love' but perhaps it makes more sense to say that, without God, there can BE no love, that there can be no Good at all and that it is only in God that we can discover who and what love really means.
The urgency about man's need for God can perhaps only be properly expressed by extremes: hell is life without God . . . which isn't to say that atheists and doubters live in hell: they certainly don't because they find God all around them whether they call Him that or not. . . but it is crucial for man's true happiness that he find God in his life if he is to truly discover who he is and why he is and what his place in the universe really signifies . . . .
the call of God comes many times in each person's life (He never gives up on us) and we have the power to answer that call or to evade it each time.
To sum up, it isn't so much about 'love' because man doesn't really do love properly: it is first and foremost about a relationship with God who can then teach us how to love because it's His own speciality . . .