Kill VPs work on a pro-rata basis where you'll get a proportion of the VPs depending on what proportion of the set percentage attrition you accomplish. In your example to get 25 VP you'd need to kill 35% of the enemy force - chances are that 1000 men just didn't form a large enough proportion to get any points at all. AFVs and guns are also included I think - I'm not sure of the exact calculations performed, that's more Dave's territory.