Not really sure who the voters are that went from Hillary Clinton (48.2%) to someone other than Kamala Harris, but I'll let that go, Romney will of course do significantly better than 12% in Idaho, Utah and Arizona, and possibly in California and the Northeast. But that's Trump from 46.1% to 39.4% which means he only has 85% of his previous votes. Let's give him 90% of his 2016 votes instead to take care of Romney's strengths being in states we know Trump will lose and the ones that Romney wins.
The Democrats keep NH, flip (in order from closest to farthest) Michigan, Pennsylvania, Wisconsin, Florida, NE-02, Arizona, North Carolina and possibly Georgia (which Trump took 50.77% to 45.64%) and I'm unsure about Ohio which Trump won (51.69% to 43.56%). The next ones after those are Texas, Iowa and ME-02 which Trump will definitely keep.
Giving Georgia to Harris and Ohio to Trump gives a final result of 325 Harris - 203 Trump - 10 Romney.