What will happen to the gravitational force between stars as the universe continues to expand?

In a galaxy, the expansion of the universe actually does not have any effect, because the force of gravity is enough to kinda keep the celestial bodies in their orbits.

Now, the expansion can be seen between galaxies (according to the Hubble's law, the far away is the galaxy, the faster it seems to move away), so the forces between stars actually will not really change, and the forces that the stars are experiencing by bodies in other galaxies are almost depreciable, so nothing will happen.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.