Hi Srdjan,
You can configure the leading, primary and secondary item at the K2 Parameters for the layout grid under the Category Item Layout. In your case,
Leading Count : 1
Columns for leading : 1
Primary Count : 1
Columns for primary : 1
Secondary Count : 2
Columns for secondary : 2
Links count : 0
As for the having the module in the category view, you might want to view some discussions here , here or here (Modules Anywahere by NoNumber.nl )
K2 Rocks \m/