Hard to tell with how high Wallin had his trunks. I think Chisora was aiming no lower than the waistband, and certainly wasn't aiming for the scrote. Wallin was terrible anyway. Chisora should have hit him in the nads (ok, not really).
It's better to take a chance and get caught with something big whilst trying to win the fight than cruising to defeat.
Easier said than done. Wallin doesn´t have that in him, at least not when hes in a one sided fight. Plus it´s not like he knows how to just go for it, hes never done it. Wallin is clearly aware of his limitations.