To find the number of even factors, we can multiply the number of odd factors by the power of 2 (not the power of 2 + 1!!!). For 540, we have (3 + 1)(1 + 1)(2) = 16 even factors.
No you have to make sure to line up the decimals when subtracting them. Do not just line of the numbers, this wills get you the wrong answers. Hope this helps. If you need anything else just call for a helping hand.