Loan Payoff with Variable Payments

I am looking for some help with being able to enter data and be calculate a loans payoff with variable payments being made to determine additional charges that were incurred because the loan was not paid in full with the agreed upon monthly payments. Yes this will be used in a divorce case to show that the my party (MOVANT) paid additional monies on the loan because the REPSONDENT failed to pay full amount that was agreed upon. My client was forced to pay additional monies of the life of the loan because of his failure to pay the full amount. The court only see's $25.00 a month ($300.00 a year) not being paid for 5+ years, but I need to determine how much additional interest was charged my client because of that.

What I know:
Loan Amount is $8289.37
Interest Rate is 8%
Payment should have been $250.00 a month
Loan originate date 07/20/09
Pay off date was 2/20/15
Loan payoff amount on 2/20/15 was $1200.30

RESPONDENT only made payments of $191.00 instead of the agreed upon $250.00 In 2013 my clients payments to RESPONDENT went down to $225.00 a month but REPONDENT still only paid $191.00 towards loan
** a couple of times he only paid $100.00 or skip payments too adding to the length of the loan even though my client paid him her court ordered amount.
See how complicated this gets. Court says we have to prove how much additional monies were paid by my client (short payments & INTEREST Payments) because RESPONDENT did not make full payments.

Can someone help determine that.
THANKS !

Its very difficult you should be hire a charter accountant for this solution,because who knows that how can be adjust the difference of $59