Our Moral Responsibility?

Just a few questions on The Singer Solution to World Poverty and a few connections and comments on a video entitled "Four Generations." Here's a Link to the video: http://www.thompsonjazz.com/movies/waterbuffalo/flash-hi.htm

After reading Singer's essay, I had mixed feelings of sadness, anger, regret, hope, loss, and skepticism. Here's a couple of questions I had after reading this essay.

-What is our moral responsibility for others who aren't as fortunate?
-Should it be considered a choice or an obligation for those who are more fortunate than others to help people that are less fortunate that they probably don't even know?
-If it is an obligation or moral responsibility for those who are more fortunate than others to help out the less fortunate (by donations, public service, community projects, etc...), where does the responsibility end?
-If it is a choice, can other people (who did help) blame those more fortunate that made a choice not to help the less fortunate for not helping out? Do they have the right to?
-How much responsibility is too much?
-Could we really change and touch the lives of those we help out significantly?

After watching the video (link is up on top, if you didn't watch it and are reading this), I felt good that a family who needed a helping hand got one that was maybe more than they might have ever thought they would get in their life time. It felt...well...satisfying. This video had some connections to Singer's Solution to World Poverty. A connection that I made was that donations from people in the United States were gathered and sent to a less fortunate and desperate family really did help that particular family, in a big way. In Singer's essay, he talks about how our donations could make a difference and would give us moral satisfaction. After watching this video and having the feeling of goodness, but also having a ping of regret for not even participating in this one particular satisfying international project, in me, I do believe Singer was right. Another connection to the video I made with Singer's essay was for how little we could change someones life. In Singer's essay, he talks about how for as little as $200 we could change a sickly 2 year old into a healthy 6 year old. In the video, for as little as $250, we could buy a poor farmer in China a water buffalo to help plow his fields and help out with daily chores for about a 15 year span. It is quite amazing. It makes me wonder what I should or could do, which is probably the whole point of both the video and Singer's essay.