"Whoa, hold on, doesn't that sound more like some kid that's been kicked out, left out in the cold?" (or something to that affect)
What may have tripped you up here is the word 虐待. I'm sure your dictionary tells you that it means "abuse", but in reality it refers to any mistreatment of children, including neglect and other non violent forms of abuse, so just because that word is there doesn't necessarily mean that the child was beaten up. Locking a child out of the house is considered 虐待, and is also actually quite common in Japan.
"Pfff, I didn't take you for the type to pocket a box of chocolates"
His friend is busting Kouji's balls because he took home a box of chocolates without knowing who they are from. This makes him a dickhead for two reasons. Firstly, it's just considered rude to do that in Japan, the proper protocol would be to leave them in your desk until you find out who they are from, so you will be able to give that person chocolates in return on white day
, it's akin to borrowing without the intent of giving back. Secondly, if he didn't know the girl, there is a chance that she did put them in the wrong desk, making Kouji a thief, and this is compounded by the fact that he didn't bother to find out who the chocolate giver was.
Something like "Oh shut up, you're no saint yourself!" or "What are you, my mother?"
風吹かせる is an idiomatic expression which means "to act like". Kouji is telling his friend not to take the moral high ground with him, to not act like his big brother and tell him off. 風吹かせる is almost always used in a negative sense, like this example. It has connotations of someone acting as person of knowledge or authority when they don't really have anything to back it up
"What was I supposed to do, stand there in front of everyone asking if they knew what it was and let everyone know what an idiot that girl is?
I think the first part to address is that バレンタインに知らねえ女 doesn't mean a woman who doesn't know what valentines day is, but something happening with a woman you don't know on valentines day.
Secondly, it's actually a pretty weak excuse on Kouji's part, but his reasoning is that if he were to ask who's chocolates they were, it would embarrass the girl that gave them to him.
Maybe I should try out for this thing, translating manga seems a whole lot more interesting than fucking business proposals and advertisements