I think that there is a couple of places to cut down the budget and make it less tight.
Groceries $650 is way to much. You should be able to cut that down by $200 atleast. There are a lot of ideas on frugal cooking etc
Mobile phone $155 a month change plans
Also can you adjust your tax witholdings on your husband's check.
Are you getting a tax return back this year? If so put that towards the repayment plan.
You also may want to consider working at home. There are some legit work at home customer service jobs that you can do overnight while the kids are sleeping.
Legit work at home jobs