If you are a Joint Filer you should enter the information as it is on your Tax Return. Essentially you and your spouse share the AGI from a Married Filing Joint return so you would enter this value to calculate your 1040ES. The IRS States as such regarding Estimated payments:
"If you don’t pay enough tax through withholding and estimated tax payments, you may be charged a penalty. You also may be charged a penalty if your estimated tax payments are late, even if you are due a refund when you file your tax return."
https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes
The Federal Withholding from your husband's paycheck is also considered towards this estimated Payment amount during the year. Nevertheless it is advisable to make the highest Estimated Payment Possible. This will help in keeping Penalties away but above all provide Peace of Mind.
