I think he loved Harry as much as he loved Dumbledore, though he never showed it. He disliked Harry for being James Potter's son, but loved and cared for him even more, because he was Lily's son.. her last living memory...

Yeap, definitely Liy and Dumbledore. Though he also seemed to have a friendship of sorts with Lucius. That's probably the reason why he was nicer to Draco and why Narcissa felt she could go to Snape for help with Draco

Ofcourse !!

certainly

I can't really pick any one of them, because I don't believe he ever loved Dumbledore; I mean, Dumbledore was the kinder Master, but to Severus I don't think he was much different from Voldemort, so no, I don't think he loved him.
And I quote from the Prince's Tale:
"You have used me."

"Meaning?"

"I have spied for you and lied for you, put myself in mortal danger for you. Everything was supposed to be to keep Lily Potter's son safe. Now you tell me you have been raising him like a pig for slaughter--"
So yeah, I don't think there was any lost love between them.

I don't think he loved Draco two, I guess he was just trying to protect him, I think he did the vow for Narcissa, who he admired I guess or held very close, but not loved her.
I guess Lily is the only person Severus ever loved. I don't think Severus is the kind of person to spread his love all over the place, and I guess Lily was the only person that received that love.

Of those shown, Lily and Dumbledore.