First of all He wouldn't be much of a God if He didn't want that for us-and eternity with Him in heaven might be a bit of a grind

. The Church has always taught this, related at least to 1 Cor 2:9. Also, look up the word beatitude and its etymology; the church has also taught that God wishes to share in His own beatitude/happiness. He's a good God, His glory is a reflection not of an aloof superiority but flows from the goodness and love that He
is-and inherently wants to share. What we have to understand is that God is infinitely, ineffably
good and loves man lavishly and wants the very best for him-always has; God's on our side while enmity came from us, not Him, even as He allows us the freedom to wallow in our selfish, prideful foolishness, eternally if we wish. Anyway, Jesus came as a suffering
servant, remember, and when we see Him we see God.
Most of the suffering probably comes because we pursued our own happiness instead of living God and living man.
Yep, but not only that. Try losing a child or suffering some awful illness or being a victim of
another's sin or wrong-headed pursuit of happiness IOW-and you may well have. And these things can be used as well-to break stony hearts, to help us reject this world's ways and in any case help see our need for and dependency on God.
Suffering can also cause believers to fall away. It happens.
Yep. Never know; it can happen either way.
Correct. So why do you throw in the selfish “happiness is his desire” stuff?
Because, if we're honest, we'd agree with the church that we all desire happiness-it's behind much of what we do, many of the choices we make-it's simply innate to want it, and it would certainly be bizarre to pursue its opposite-unhappiness. Happiness is our "homeostasis" so to speak, where we want to be internally and no more selfish in itself than simply wanting what's good and right for ourselves, even if we
can be selfish in pursuing it. So even someone using drugs or pursuing wealth or even just some hobby is looking for that elusive quality. And the more we let go and let God, the more peace and happiness we experience, relatively speaking to the extent that this world allows it. The ultimate happiness for a human, and that which finally totally captivates his will so that he desires nothing else except God first above all else, is the immediate vision of God, that which causes us to seek His face to begin with as Scripture directs us to do, and that which is fully consummated when we finally "see" Him "face to face" and know Him fully as per 1 Cor 13:12. As Aquinas put it, "God, alone, satisfies."
Well actually obeying God in detail is obeying God. I mean loving God is vague until He asks you to do something or refrain from doing something.
Loving God isn't vague; Jesus didn't teach the Greatest Commandments for no reason; love is the very New Covenant reason for obedience, the right motivation for that obedience as opposed to blind insincere drudgery or sense of obligation based solely on fear or legalism. Love should be every Christian's goal; most vagueness about it would be due to the fact that we don't yet
know it as well as God desires us to-and will help us to. Anyway, here's Basil of Cesarea from the 3rd or 4th century speaking:
"If we turn away from evil out of fear of punishment, we are in the position of slaves. If we pursue the enticement of wages, . . . we resemble mercenaries. Finally if we obey for the sake of the good itself and out of love for him who commands . . . we are in the position of children."