#3
i dont know if you were saying that song's NOT cheesy, but if you read the lyrics of that song, they're packed full of cheese.

happy songs are hard.

just write what you want and deliver it well. it's more about the delivery than the actual words. although do your best to keep the lyrics cheese free. just dont get TOO stressed about it.
#4
try instead of using the major scale use something like the mixloydian or dorian or maybe lydian, those scales are quite neutral in happy/sad sounds except maybe the dorian