Harley will forever be in her debt. He might be inclined to share his special stash of whiskey and chocolate.
Their mother frustrates me. The one mom I did like they ended up killing off (though her kid was a total ass and I'm glad they DID kill him off, though it felt more like copping out bull crap). Alicia is incredibly loyal and she has a good heart, though it's probably bruised from all the crap she's had to deal with. I'm sure Negan can sense that in her too. Harley is ALLLL about enjoying life and having fun. I can see him dragging Alicia into that.
Harley doesn't get why people think Negan's this huge asshole. Okay, yeah he gets it but seriously, like you said, there are totally WORSE men out there and compared to them, Negan's a freaking teddy bear. I don't know if she's lucky to be part of their complicated family but she could be worse off.