Numbering, in Word, is quite finicky!
You cannot use Format Painter between levels!
If you use automatic paragraph numbering or bullets read Shauna Kelly's directions on numbering and bullets. Start with [How to create numbered headings or outline numbering in Word 2007 and Word 2010]. For large documents you must follow these directions or you will lose your hair!
(Mac version: https://www.brandwares.com/bestpractices/2016/06/outline-numbering-in-word-for-os-x/)
This may seem a bit convoluted at first, but it really is not. Just follow the steps. Shauna Kelly's instructions use the built-in heading styles, but you can use any existing paragraph styles including your custom styles. There are, however advantages to using the built-in heading styles when you create a Table of Contents. Here are some more advantages: [Why Use Word's Built-In Heading Styles? by Shauna Kelly] Note, you can modify these built-in styles to look exactly the way you want.
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The basic idea is that the numbering is set using the Define MultiLevel List dialog with each numbering level being attached to an existing paragraph style. Once you have this set up, you should not use the buttons for numbering in the Ribbon but rather apply the appropriate style for that level.
You can save a document with this as a template for future documents if you want so you will not need to do this every time.
If you are going to use the built-in list styles, start with the ones that say Heading 1, Heading 2, etc. Do any modification to Indents or the appearance of the numbering in the Define New MultiLevel List Dialog. My advice is to follow Shauna Kelly's directions to get something that will stand up to editing.