1. He realizes he loves Buffy awfully fast. (The Initiative)
Same as Angel. Same as Xander. Same as Oz when he first glanced at Willow.
2. He doesn't recognize Spike just because he is wearing a different shirt and faking an American accent. (Doomed)
I don't remember, but did he ever see Spike face to face?
3. He thinks Professor Walsh's attempted murder of Buffy had to be "a test." (Goodbye, Iowa)
Prof. Walsh was like a monitor to him, it's hard for him to just accuse her. He sure will try to find some explanation to what she did and once he realized she tried to kill Buffy, he left the Initiative, and that's in itself was a great sacrifice.
5. He sleeps with Faith/Buffy even though Tara picked up on something wrong. (Who Are You)
Tara read Faith's aura. Why not blame all Buffy's friends who didn't recognize that this Buffy wasn't Buffy? They knew Buffy longer than Riley did.
6. He can't accept Willow's relationship with Oz. (New Moon Rising)
It was hard to grasp at first. Hello, a girl dating a werewolf? But then he came through and he saved Oz from the Initiative, he was heroic.
8. He refuses to get heart surgery even though every person who cares about him is begging him to. (Out of My Mind)
He was having a dilemma. He didn't want to be normal, because he thought Normal Riley would not be interesting to Buffy. It's a matter of insecurity.
9. He lets vampire women suck him while Buffy and Dawn are going through hell with their mom.
Buffy never needed him. He was acting out. He tried being there for Buffy but she just shut him out. And he wanted to know what it felt like being bit by a vampire.
11. He doesn't stay in Sunnydale and try to work things out. (Into the Woods)
Because Buffy didn't give him a reason to stay. She never needed him anymore. And he didn't feel that she loved him, so he took off.
12. He doesn't look out the window when his helicopter is taking off. (Into the Woods)
Because of the loud sound of the helicopter? Seriously, how could he hear her?