What mechanism allows three spacial dimensions? Answer me this and I might be able to answer your question. Besides, I'm really just trying to give form to some of our observations.
As far as the interaction, warping of space-time. Remember, from our perspective, and the perspective of our localized baryons, the 'anti-gravity' poles 'appear' to not exist, and if we could observe them through the curvature of the tesseract (hyper, four dimension) sphere, it would appear to occupy infinite points around us. (However, we would then be able to measure its distance.) Just as if you were to stand on the north pole and look along the curvature of the earth to the south pole, or even back to yourself, a pole at the southern pole and even you would appear as this wall that completely surrounds you. Because we are unable to observe the opposite pole however, it also gives the appearance of possibly being infinitly far away... until we are able to figure out how to measure the diameter.
Also, gravity seems to work more strongly on matter than itself.
I would agree with you on the confinement of gravity, it is just that what I picture as the four dimensional hyper sphere of influence appears to be so exorbinantly large, entwined with other hyperspheres of influence, and of course appears to go into infinity from our three dimensional perspective. Just as magnetic field lines appear to go into infinity when we observe them from three dimensional space. The magnet's hyper sphere of influence however is not infinite. How to measure the diameter of said hyper sphere of influence? Well, one step at a time. Just as humans of old did not know how to measure the size of the earth due to it's curvature, or even that it was curved.
Besides, are we not trying to tie gravity with the other forces? Guess you could call this my GUT feeling. (yeah, bad overly used pun)
My suggestion, watch a youtube of a tesseract cube in rotation. Imagine one point in the upper 'tetrahedral*' cube and another point in the lower 'tetrahedral*' cube. ( as appears from our three dimensional perspective.) Draw straight lines between the two points, then as the video rotates the cube, continue drawing straight lines between the two points and imagine what appears to happen to the other lines that you have drawn.
And please remember, this is all just a hypothesis, which is based on observations; mostly of magnectic field lines and tesseract objects as well as accretion disks and well, you get the idea... and not being content with thinking just three dimensionally. :P
Thank you for your questions and for keeping me thinking!