One of the reasons Whitehead gets read at all is that it's hard to think about an unchanging GHHITS (Great Hoo Hoo in the Sky - or god of the philosophers) who has any kind of relation with things that change but does not change itself. In other words, if you're confused, you're in some very high-falutin' company.
I haven't read Augustine on time - though I must have years ago since he talks about it in the Confession. I sure don't remember what he says.
Yes, thank you. That sounds like a good way to look at it.