How does this fluid interact with matter
and cause the effects of gravitation?

Dunno how long you been readin' these threads, but it's been elucidated
in detail numerous times over the years.

Tell ya what, big guy. First *you* answer that oft-repeated 'Litmus
Test' question cogently and/or "fill in the blank" if you have a better
theory of the _cause_ of gravity.
Then you can ask your questions.