EUm yield , I think you are mixing up terms. Most often, when using yield in this case, they mean a % or just how good the "yield" is, how much you have from the initial amount.
Of course: the DNA will not "become more", I mean: you start with X DNA, it can never become more.
The "yield" can be pretty good, but it will Always be less of course.
THe DNA purer than before? Depends on what you mean with "before"... You mean after a restriction digest or? Yeah, of course...
Normally you use the ethanol precipitation indeed as a way to clean up your DNA so yeah, it should improve the cleanliness.
ok. That is what was confusing me. I just wanted to confirm the "yield won't ever improve" but the DNA would be purer than before.