Would deflecting it to a shorter orbit and slowing it have the effect of causing it to be drwan in by the Suns gravity over time?
The delta-v required to make it miss the Earth, if it's really on a collision course with Earth in 2019, is probably far beyond our capabilities.
Why wouldn't a large explosion at an anlge not change its course and orbit?
No, it would kick it into a different orbit. Unless that orbit intersects with the sun on the first pass, it will stay in that same orbit indefinitely. (Caveat: since it does make occasional passes very close to the Earth, it is possible that a slight change might put it on a course for a gravitational slingshot maneuver past the Earth, by which method it can be made to go just about anywhere. But this would require steering it exquisitely close to the Earth, taking us to the very edge of catastrophe, which is what we want to avoid.)
Why wouldn't a large explosion at an anlge not change its course and orbit?
Well, there's large and then there's large. What seems a large amount of energy to us is terribly small compared to the kinetic energy of this rock.