Third-party voting will probably be less than 1% this year.
I'll take that bet. How much are you offering?
My guesstimate is 3%, which most of the difference from 2016 benefitting Trump because the Libertarian vote is going to go down from their all-time high (maybe it doesn't if Amash is the candidate) and there's no anti-Trump McMullin candidacy this time. I think most of the anti-Trump 2016 right-wing vote is going home because anti-Trumpism on the right has declined. (I had a thread about this a couple months ago I started which goes in much greater detail.)
As much as I'd like to disagree with you, I can't. I think there were a lot of conservatives that didn't think Trump would be conservative that voted for McMullin or Johnson that are going to vote for Trump this time. I think the fringe left is going to vote for the green party candidate.
I don't think it's going to be any different from 2016 though. I mean Stein got 1%, which is doable under Hawkins. Joe Biden is not as hated by the left-wing as Hillary Clinton was although some people do. So maybe if Hawkins only gets votes from more DSA/Sanders or nothing clienteles, say 0.7% perhaps?
The Libertarian Party nomination is really the biggest monkey wrench in this discussion. While if you're really a principled small-l libertarian, the Republican Party under Trump have completely left that philosophy and it should increase the size of the Libertarian Party base vote and membership, the difference between say Justin Amash and some of the other options at their Convention are huge as far as number of votes. Really the Libertarian Party have been able to stop gadflies from getting their presidential nomination lately, with the last gadfly that got the nomination arguably being Badnarik in 2004. But you still have that underlying threat in the neverending battle in the party between the more pragmatic and the more purist.
Wouldn't surprise me if there are some GOP or Democratic Party agents at the Libertarian Party Convention even as voting delegates acting covertly to try and nominate the candidate more beneficial to their cause. They've each certainly done worse in the past.