F_1_2 = F_1p_2 (by shell theorem) = -F_2_1p (by 3rd law which is explicitly true for Newtonian gravity) = -F_2p_1p (by shell theorem) = F_1p_2p (by 3rd law again), and so F_1_2 = F_1p_2p QED.Of course, the interaction between the 2 masses can break their spherical symmetry and then neither shell theorem nor its corollary apply at least NOT exactly.
Birkhoff's theorem tells the same story. Any spherically symmetric object's gravity is exactly the same as if all its mass were concentrated at a point at its center for objects outside of its radius.
For example, a 1 solar mass black hole and the Sun have the same gravitational field as long as you are ≥ 1 solar radius from their centers.
To conclude, the powerful gravity and exotic effects of a black hole only occur when you are relatively close to its event horizon or at least closer than the radius of an non-black-hole of the same mass as the black hole.
So black holes are NOT monsters of gravity swallowing eveything in the observable universe.
Actually, it has been shown that gravity of the size of Earth surface gravity (fiducial value 9.8 N/kg) probably quantizes atomic states like other forces (see Evidence for Quantized Gravitational States of the Neutron, Frank Rioux, 2020; Quantum effects of gravity, Thomas J. Bowles, 2002, Nature; and for the research article itself, Nesvizhevsky et al. 2002, Nature). However, this result, IF VALID, is just what we thoroughly expected and does NOT tell us more than confirming what we thought. So it's wonderful, if valid, but does NOT elucidate quantum gravity very much.