Hi,

– sorry it is not possible to center portfolio items,
– to change the column count, edit js/main.js in theme folder in a text editor and at line: 345, you will see columns values for browser widths;

var viewports = [ {
		width : 1200,
		columns : 5
	}, {
		width : 900,
		columns : 4
	}, {
		width : 500,
		columns : 3
	}, { 
		width : 320,
		columns : 2
	}, { 
		width : 0,
		columns : 2
	} ];