There's a possibility that the totals for Johnson/Stein could vary by 1-2% based on whether people think the election is close or not. Essentially, the less "risk" there is to voting third party, the more likely people are to do it. You might not think Clinton cares whether Johnson gets 4% or 6% or 8% as long as she still wins, but believe me, she does. 5% of the vote gets the LP federal funding in 2020, which makes a big difference and presents a serious threat to the two party duopoly if it is used properly. Yes, it can just result in endless infighting and implode the party, but Sarwark (LNC chair) seems fairly intelligent and is definitely popular enough to pull some strings in the right direction (He was re-elected with 65% of the vote at the Convention this year).
Yes, but good performance can help to get those voters stay/back.
I just don't buy that Hillary would on purpose doing worse (XX% of her best performance).