"To a degree it can be argued that he goes after Buffy because Angel loved her, but I doubt it. Angel is important to him and he does to a degree lurk in Angel's footsteps, but I think it was Buffy who inspired him "
I really agree, if Spike's feelings for Buffy were based only on Angel's desire for her then he would have lost interest when Angel left town... but in fact Spike becomes more obsessed.
After Spike does 'go out in a blaze of glory' at the end of Buffy's S7 I think he felt that anything else would be anticlimactic, that perhaps his relations w/Buffy had peaked.
Even if he hadn't returned as a ghost in Wolfram & Hart, I think that Spike would have still wanted to follow Angel at that time. Because I think Spike was wanting to explore this whole 'hero' thing....
but that would be a different discussion (one about siblings/brothers). I really loved your points about Fathers & boyfriends leaving.... and your discussion about women being pimped out by those Fathers/boyfriends.

I've been rewatching Firefly today and of course Joss carefully made Inara's situation independent, in fact Mal's disapproval serves several purposes since he is not only seen as jealous of her sexual activities, but also he cannot be seen as pimping her in any way (in fact she complains that he takes jobs in remote locations where she can't get work).

And now in Dollhouse EVERYONE is pimping Echo out...