Paid amount and Remaining balance on customer invoice

Hello experts

My client asked us to modify their invoice to show total paid amount and remaining balances.

following is the modified design of the new report .

I know the path of the remaining balance of the customer, but I cannot find where I can get remaining balance & paid amount of a certain invoice.

Please help me with find the AOT path of the remaining balances & paid amount  of  invoices.

Thank you!