What makes Paul Johnson's view (assuming your quotes in 8 are representative) inaccurate is not his anti-Catholicism, on which, I agree, there is room to argue, but their nauseating, banal, 20 century political correctness.
Indulgencies? We've been conditioned to knee-jerk here. A good Catholic, or a good student of the Middle Ages won't. An indulgence is granted even today for certain charitable work. It discredits, or adds "complexity" to the history of the Crusades just as much as the US congress awarding medals to good soldiers.
Migration? Hardly anyone settled in the Jerusalem Kingdom. There may have been a secondary effect of settling the Balkans, already Christian, by some who dropped from the Crusade midway. Like it or not, it is not a motivation but a side effect of the Crusades.
Racial arrogance? Guilty as charged. They did not have affirmative action or busing either.
Ecclesiastical control? Or, as Johnson himself explains, the church needed to channel religious enthusiasm to productive ends. Good for them, that is what an institutional church is for.
If this is all there is to his book, it is useless spin.
As you wish. This was a minor discussion in his book, which is concerned with two millennia of Christian history.
Another poster later on this thread takes some pains to debunk Johnson's efforts, which perhaps will confirm your skepticism of it.