I'm having trouble with #3 and #4 to be honest. 'Happy' and 'sad' are too strong emotions to be elicited by a song.
Taking a stab at it:
03: Song that makes you happy
Walking on Sunshine - Katrina and the Waves. Basically I wouldn't listen to this song voluntarily under most circumstances, seeing as how it's a little annoying, but it is the most upbeat song in the world so if you were feeling blue I can see how this song might be helpful.
Incidentally, I heard once a version of this performed by some tragic Disney-type singer who was trying her darnedest to make 'Walking on Sunshine' sound sexy (I'm waaaaalkin' on sunshhhhhine, *orgasmic moan*). Maybe I'm misremembering that though (I hope I am).
04: Song that makes you sad
Hide and Seek - Imogen Heap. I think this song is supposed to be about the breakup of a family from the point of view of a child, is that right? If so, it's a lot better than Dilemma (which covers the same topic from a different POV). The lyrics are pretty sad, although I guess it suffers a bit from being 'the song from Speak For Yourself that people have heard'. Also the Jason DeRulo thing.