Q1: what does "tiger"here 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.”
She put her hands to her head, did a little dance in place. “Dinner date. I have to wear heels to make it look real. Okay, okay, I’ll stuff some sneakers in my bag, change shoes for the jog back. And don’t give me that look. Footwear’s important.”Q2: what does "then——crap"mean?

Question

Q1: what does "tiger"here 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.” 
She put her hands to her head, did a little dance in place. “Dinner date. I have to wear heels to make it look real. Okay, okay, I’ll stuff some sneakers in my bag, change shoes for the jog back. And don’t give me that look. Footwear’s important.”Q2: what does "then——crap"mean?

Answer

Tiger can be a name. It's not common, but some boys are called Tiger!

Tiger can also be a nickname.

In this case it looks as if she is calling him 'tiger' just on that occasion because he is being 
aggressive.

Crap is simply a swear word. She has forgotten about something, suddenly realizes, and says, "Crap!"

Answer

"Tiger" can mean someone eager, macho, virile. "Easy, tiger" means "calm down, don't be in a hurry."

Some equivalent colloquial phrases would be: "Easy, cowboy," or "Cool your jets."

"then circle back on foot to the south side, then— Crap" is an interrupted thought, followed by an expression of irritation. She is going to complete the plan, then suddenly she remembers her dinner date. The dash is the place where she suddenly remembers, and stops talking. She's annoyed because she realizes her plan won't work, so she says "Crap." Similar examples:

"I'll take the 9 a.m. train into Philly and--Oh, hell, that's a Sunday, the trains won't be running."

"Ill meet you there, and it sounds pretty formal, so I guess I'll wear--Crap! my suit is at the cleaners."

Answer

a tiger is an animal but sometimes people call someone "tiger" if they are being too excited, growly, aggressive, and flirty. its not that commonly used and you defiantly dont need to use it so dont worry!

crap can be used as a swear word but its not as rude as other swear words, like "fuck" and "shit" so in this sentence 'then--- crap" she was talking in a sentence but then she realized she had the dinner so she used the word "crap" out of shock

sorry im not good at explaining