I'm just speculating here based on my limited knowledge of the subject, but I think that astrology has less to do with any specific force acting on people than it has to do with viewing the universe as having an inherent order to it. I'm close with a number of Hindus (highly educated ones; all manners of advanced degree) who take astrology very seriously. From what I gather, they use astrology as God's way of telling us what God is doing in the universe. Some may say that it is due to this or that specific gravitational or electrochemical force, but I think that's a superficial reading of it. My interpretation is that God has ordained that the world be so, and God also made the heavens. The heavens therefore are correlates to all that is God's plan. This is a simplistic and perhaps incorrect reading of the text, but it's the best I got. Anyway the point is that we can throw out the fact that G is disappearingly small over great distances, because it's not really the point. Apologies if I'm telling you stuff of which you're already aware, but I think this point is lost on many people, especially young people who haven't yet figured out that there's more to life than the measurable.