No matter how horrible Horrible Hillary is
I still think Trump smacks his (thankfully well cushioned) head on the ceiling at about 40%.
And I don't think Johnson/Stein can peel off 20%. Maybe 15 though.
So maybe Clinton 45, Trump 40, Johnson 10, Stein 5.
In that case the dems pick up maybe 4 senate seats, maybe a dozen house.
But even if Hillary goes Full Clinton and becomes a stealth Republican I don't think that works any more- the degree of personal animosity is too great. If she gave Republicans everything they wanted they wouldn't take it, fearing she'd try to share the credit.
Hard to imagine what pleasures will have fallen upon our blessed land by 2018 but the SCOTUS will probably be down to 4 or 5 judges. For The Faithful, history says that particularly in troubled times the sitting president's party loses in the mid-term. So don't despair- you can drill on the village green but I wouldn't attack until after you see what happens then.