You might be out of luck with this one. I would suggest placing the dynamites near each gas structure (where you have them is fine), as well as one more where the upper blue dot is. This should take care of the right side, although more than likely there will be a few stragglers.
The blue mines can try to control the 3 left entries of the zombies, on the road about 2 buildings from where they enter. If you're extremely lucky, you can catch the stragglers on both the left and right with the mortar (cannon?), but agent86 is right, this map might not be possible with your items.
Your setup looks pretty good to me too... so you might have to scrap this guy. Getting the stragglers without foot patrol or snipers is impossible for some setups.