Interesting discussion.
The push/shadow/particle models of gravity are thought provoking and initially seem to be viable, but then seem to .... well ... fall down!
I find it especially hard to conceptualise these models for Black Holes.
Info on the following site is a bit of a mixed bag, but some of the questions are valid and much of it is thought provoking.
http://www.topology.org/sci/grav.html
I applaud people who question & challenge theories and try to improve on them ... it's like a breath of fresh air. Sometimes we have too much faith in conventionally held views (eg. gravity and cosmology models) and get too lazy to challenge and improve on them.
Re explanations for an interested teenager:
- start with Wikipedia enty for gravity
- It summarises the development/evolution of various models
- As for the "why" of gravity, I just enjoy the mystery for now
(while efforts continue to find links with electromagnetism and/or quantum theories)