Hello,
I will be including a link for a more detailed explanation that you can have for future reference. The answer to the first question is yes he should make quarterly estimated tax payments. If you wait until the end of the year to pay the self-employment taxes the IRS may charge you a penalty. The dates that the payments are due to the IRS are 4/15, 6/15, 9/16 and 1/15 of the following year. As an example the 4th quarter estimated tax payment for 2023 will be 1/15/2024.
Yes you are correct that your husband is the only one required to make estimated payments on his income your taxes have already been paid.
https://turbotax.intuit.com/tax-tips/self-employment-taxes/a-guide-to-paying-quarterly-taxes/L6p8C53...
https://turbotax.intuit.com/tax-tips/small-business-taxes/estimated-taxes-how-to-determine-what-to-p...
https://turbotax.intuit.com/tax-tips/self-employment-taxes/tips-for-paying-estimated-taxes/L1nDU0sUs
The best way to pay the estimated taxes is by creating an account at IRS.gov where you can pay digitally. When you open their site type "estimated tax payments" into the search bar.
Hopefully these links will help you moving forward
