I guess that it just won't go back far enough, will it?
[...] why don't you take Kara and Lauren [...]
Aaron bitterly accuses Abe of coveting his family--I would say that you are correct in that Abe both loves Kara, and envies Aaron's home life. Remember that Abe lives alone in an apartment and does not have a family. I believe that Aaron is taunting Abe by saying that no box can take Abe far back enough, to a time before Kara was Aaron's wife.
You can each keep a set in a hemisphere.
Aaron mockingly suggests that Abe take Kara and Lauren with him in a box, then live with them in one half of the world, while drugged Aaron can keep his "set" in another half. (Of course, Abe would then have to prevent his previous self from taking Kara and Lauren.)
[...] show you what I'm capable of [...]
This is a threat--Abe is saying that you haven't yet seen the worst that I can do. If you come back, I won't just try to get into a failsafe, I will outright kill you.
[...] don't come near them. Any of them.
I would say yes, Abe meant Kara and Lauren as well. Abe does want to protect them, and he does not want Aaron to interfere in any way. Abe has already seen the destructive results that Aaron's interference have brought about--not only has Aaron risked his life in stopping the gunman, he has drugged an earlier self and stuffed him in the attic. Imagine if that Aaron had freed himself on Tuesday night and stumbled down to where Abe, Aaron, and Kara were talking, gathering laundry, drinking beer, and eating cake.
Abe wants the Aaron that he has this last conversation with to completely disappear from Kara and Lauren's lives.
