In my experience, the only reason to have a rooster is if you are attempting have chicks. With only 3 hens, the rooster will constantly be attempting mate and will probably hurt or kill the hens. They spur the hens to hold on and it will rip the hens up and some times it will get infected...
Try a killing cone, I use old detergent bottles, wide mouth, put the bird upside down ( head thru hole, wings are constricted so they don't run around like a chicken with their head cut off) then use a box cutter to slit their throats. They bleed out, quite calmly without damage to bones or meat.
