You can purchase Excel/Office for Mac. They sell a home and student version of Office if you don't like the subscription model.
There is no stepping through nested IFs to find a syntax error. Nested IFs get messy quickly. You might try using the IFS function instead.
If you try to format a cell that has data in it that does not match that format, the format will not "take". If you type data into a formatted cell and that data does not match the format, the cell will revert the format to Automatic, possibly with some settings (such as currency settings if you typed a currency symbol and some digits). Excel will change formats, too, in many cases.
Numbers align by default to the right. Text, including text "numbers", aligns by default to the left. That is usually the first clue if a number is an actual number or is text. If the format is Automatic and the cell has a number in it, the format should also have settings for decimal places. If it does not, then the "number" is not a number. This happens sometimes with people in regions that use the comma as a decimal. If they use a decimal point, it will not be a number.
I do not know what Format Painter is but Numbers has Copy Style and Paste Style which sound like maybe the same thing. They are in the Format menu, are accessible with keyboard shortcuts, and you can add their icons to the toolbar. They copy/paste all styles applied to a cell, including the borders. It is all or none.
