Where do you get 70 points from?
In the last 5 seasons the 5th place team have got the following number of points: 65, 62, 67, 63, 65
To finish 4th you need to finish above 5th, obviously so at no point in the last 5 years would you have needed 70 points to finish 4th.
Our goal-difference is pretty good so most likely we'd only need the same points as the 5th place side to finish above them.
Our 'usual lazy performances' have seen us only 4 points off Spurs. At this stage last year we were 7 points behind, and that was after we'd played them twice so that 6 pointer could no longer help us.
In April we should make up some ground when Spurs have:
13/04 Chelsea (A) (we have Norwich at home)
20/04 City (H) (we have Fulham away)
Our next game is Utd at home where we'll probably drop points but I don't understand why you think 4 points with 12 games left is such an insurmountable gap.
I don't have a sudden boost in confidence, neither do I think all is lost. We have a decent enough chance of catching them but it's by no means certain.