re: Scenario Tump wins but dems easily get the house.

I am not sure how congress would work, but if no one gets the required 270 electoral votes then the 12th amendment kicks in and the president is elected by the house by a "Contingent Vote" which means that each state delegation gets one vote regardless of the number reps that state has. Example California and Wyoming each get one vote. The senate will elect the Vice President with each senator getting one vote.

Contingent Election of President