In a Mirror, Darkly (2) - S4-E19
Stupidity: When the Gorn attacks Archer, one of the MACO officers raises his weapon to fire, but fears hitting Archer, so he doesn't shoot. But then he attacks the Gorn with the butt of his weapon. He was close enough to hit him, he could have just stood over him and fired without fear of hitting Archer.
Stupidity: The last remaining Xindi, in desperation, attempts to release the virus over the fan, despite the virus not being fully ready. However, it seems the only reason he didn't release the virus at that time was he had to seek cover from Archer and T'Pol shooting at him and to start shooting back at them. However, he had plenty of cover from the rooftop stairwell, which was right next to the fan, and he had enough time to dump out the contents over the fan.
Answer: Warp factor has always been inconsistent and hard to pinpoint, or there's too many episodes that contradict the conversion rates. Changes were made in converting warp factor into actual speed between TOS and TNG. It seems ENT reverted back to using TOS method, which is "warp factor cubed" equals how many times the speed of light they traveled. So warp 4.5 means 91.125 times the speed of light (c). Although in "Broken Bow", with the travels from Earth to Neptune and back in about six minutes means warp 4.5 is about 86*c. However, in "The Expanse" episode, warp 5 was 200*c (instead of 125). 1 ly at 91.125*c is about 4 days, but 100 ly would be 400 days.
Bishop73