Your credit score is a 620 and your wife’s fico score is a 643.  If your score falls during your application process, there is the possibility you will not be able to refinance into a favorable program.

My advice is:

• Don’t apply for new credit of any kind.  Applications for new credit drop your score.
• Do not run your balances on credit cards any higher than what they are currently. Even if you make every payment on time, credit scores can drop if balances go up.
• Don’t miss any scheduled payments.  This is the biggest one to watch.