WOW he looks frightened of humans , this is not an attractive trait. Got to have some back bone.
Just to be clear having back bone and just being an insecure mouthy jerk are two very different things. Also retreating into your insecurities and never confronting issues bad quality for filling the role of headship.

Now about this dude...
This is a tough one, because you don't know why he is this way. It's going to be difficult to try and counteract this tendency to "cower" with out understanding it's origin.
What if he used to have a pair and somebody just broke the man down?
Try just engaging him in conversation see what's there, for a start.
It's nice that you want to help though, hope it works out! ;)