"I really despised how he went to Spike and physically threatened him. Spike can't fight back - that's such a lame, bullying thing to do!"

I really feel that this in particular was influenced by his fear of losing Buffy - and Buffy did the same, so it's quite likely he was taking his cues from her.

"he wants the 'us and them' mentality the Army provides so he doesn't have to see the grey in the world *and* in himself."

But he did get it when he saw Oz tranform, didn't he.
I choose to think the "running back to the army" was because without Buffy, he didn't have anything else, and that "marrying Sam" was an abberration by the writers.

"I don't read fics where he's slashed because he's usually written as a sadist and i have no use for that. Particularly if he's slashed with Spike"

Aw! Read mine! Go on! My version of Riley struggles with sadistic fantasies, but comes through in the clinch, and helps Spike.
And if you read it, you get a prize!