what does "given him another shot to the balls"mean?
“No, he’s being careful, not buying his personal items from the same places he bought a pound of ground beef and a box of rat poison.”
“Rat poison? I’ve never heard of anyone seeing rats at . . . Oh God.” Shock hit first, then fury. “That—that son of a bitch. He plans to poi-son Barbie? That miserable excuse for a human being. It’s a good thing I didn’t know. I’d’ve given him another shot to the balls.”
“Easy, tiger. What time’s our reservation?”
“Our what?”
“For dinner.”
“Oh. I didn’t get that detailed.”
Eli checked his watch. “Okay, we should leave about six. You worked it out with Maureen?”
“Yes, they’ll keep Barbie. So we’ll just go as we planned. Leave here with the dog, drop her off at Maureen’s, then circle back on foot to the south side, then— Crap.”

Question

what does "given him another shot to the balls"mean?
“No, he’s being careful, not buying his personal items from the same places he bought a pound of ground beef and a box of rat poison.” 
“Rat poison? I’ve never heard of anyone seeing rats at . . . Oh God.” Shock hit first, then fury. “That—that son of a bitch. He plans to poi-son Barbie? That miserable excuse for a human being. It’s a good thing I didn’t know. I’d’ve given him another shot to the balls.” 
“Easy, tiger. What time’s our reservation?” 
“Our what?” 
“For dinner.” 
“Oh. I didn’t get that detailed.” 
Eli checked his watch. “Okay, we should leave about six. You worked it out with Maureen?” 
“Yes, they’ll keep Barbie. So we’ll just go as we planned. Leave here with the dog, drop her off at Maureen’s, then circle back on foot to the south side, then— Crap.”

Answer

It means another hit in the testicles (usually a kick).

Answer

Again - it's hard to tell. 'Balls' is clearly testicles. But as for 'shot' - I don't know. I guess it doesn't mean a literal gunshot. It probably means a kick in the testicles, or a knee in the testicles. From 'another' we can assume that (s)he has done so before. Did the story mention something like that previously?

Answer

Austen's book is much more difficult than morden novel.Actually, I find this novel quite interesting... it's not that difficult if I am not that picky. but when I am reading sth, I am planning to figure out the meaning of every word and every sentence. Austen is on my list, I will read it one day,thank you for your suggestion,

Answer

Another torturous journey begins.  Reading should be much more pleasurable than this.  Why don't you read something that learners normally read, such as Jane Austen, and then you can get an accompanying study guide to help you with it.  Even native learners learn English that way.  Morever, you can make sophisticated or respectable conversation out  of Jane Austen.  I doubt if you can do the same with this kind.of writing.  Life is too short.  Spend your time and effort wisely.