Fundamental forces are mediated by gauge bosons. The known ones all have spin-1 but the graviton, if it actually exists, would have spin-2. How do they know this? How do the properties of the forces depend on the spin of the gauge boson which mediates it? I've read somewhere that the fact gravity is attractive only is from that the graviton would have spin-2, and electromagnetism can be attractive or repulsive because the photon is spin-1.
Would that mean the strong force could be attractive and repulsive since the gluon is also spin-1? (I know confinement and self-interaction means this is purely theoretical) How about the weak force, is it really attractive and repulsive at the very short range it operates at? Is there such a thing as weak "charges"?
Bosons can have integer spins. If there was such a thing as a spin-0 force mediating boson, what properties would its force have, and why? I did see discussion on whether the Higgs boson was or was not a fifth force or a variant of the weak force, and it could not act as a real force because it would have an even shorter range than the weak force because the Higgs is even more massive than the W/Z.
How about spin-3 or more mediator bosons? What properties would such a force have if such bosons could exist?