how do I make the products and subtotals of the customer's order appear on the invoice

Lastly, how do I make the products and subtotals of the customer's order
appear on the invoice.
Please see image of what it currently looks like:

I have tested a cloned version of your form and it seems the invoice is showing the products and sub-total in the email when it is attached.

Screenshot:

Please test your form again and let us know if the issue still remains.