President Obama had a super majority congress when he was elected too. Don't worry, they never last long.
I wouldn't bet on that. The vast majority of congressional districts are gerrymandered so that only a very significant change in political preferences will change which party wins the seat. Obama managed that in 2008 but Trump (and the rest of the Republicans) will have to colossally screw up to make things change significantly in 2018. The Senate is even worse, as I understand it, most of the seats that come up for re-election is 2018 are already held by Democrats.