Referencing the values of multiple cells in conditinal formatting.
 

I need help with these formulas. In cell A1 I want conditional formatting to be activated in these three conditions:

1) If cell B1 is blank and cell A1 does not = 0
2) If cell B1 is not blank and A1 = 0
3) If cell B1 is not blank and A1 is greater or less than 5 of C1

It would be convenient if it's possible to combine 2 and 3 and make the third formula:

If C1 = 0 or = blank and A1 and B1 are not blank.

Otherwise I can add the final formatting to C1 as a cross check.