And thanks for the comments on my story! I'm glad you like the dialogue and that it seems natural. It's one of the things I concentrate on the most and one of the things that bothers me the most when i'm reading other stories. And that moment you pulled out was actually one of my favorites from this chapter!
More with old man twist on the way.... hopefully with Ennis by his side, Jack will find a little more courage and that asshole will get what's coming to him 
When the dialogue and the non-verbal communication that comes with that are good and creatively written, then the story does really come to life, that is what I was always being taught in university during creative writing and screenwriting classes and it's what I always concentrate on too when I write short stories.
In this case, I could really see that happening right in front of my eyes:
Jack sighed. It turned to a hiccup in his throat and he smiled wide, giggling. “A lot. A whole fuckin’ lot.” It's sad and hilarious at the same time, well done!
And yes, I was thinking that having Ennis by his side will give Jack more courage to finally stand up to his father (but he's not going to let Ennis do it for him I think...) and give him one hell of a verbal beating. Wow, tough dialogue on the way for you to write! :-) Bet you will do fine, though!
