No, I doubt he would even do that much better. Gonzalez did as well as he did not because of Trump.
I think Baker would have hit 70% if this was a Clinton midterm. I'm sure there were some Democrats who approved of Baker but couldn't vote for someone from the same party as Trump.
In reality he got 66.6%, so hitting 70% would not be that much better in the grand scheme of things.
Any Democrat who approves of Baker but didn't vote for him probably isn't voting for any Republican anyway. The only improvement Baker would have made if it was a Clinton midterm would be due to the enthusiasm gap being reversed. And that wouldn't have been nearly enough to win Cambridge, Somerville, Amherst, Northampton, Leverett, Wendell, Great Barrington, etc.