Interesting. I definitely agree with you that many people - particularly those who are struggling to survive in some way - will need to help themselves first. Once somebody reaches a certain level of comfort, giving to others then starts to provide even more happiness I think. Although it's certainly up for debate!
You are absolutely right that any "global" measure of happiness is too broad to be useful. I'll have to think about this one.
Yes when one has more he’s more likely to shift the idea of what makes him happy and he may incline to helping others more! That’s a good point, although again, not always. I’m really happy that I made you think more deeply about the issue :).