How is your husband doing?
Stopping cold turkey can cause very rough withdrawal symptoms. It's always better to wean with the help of the doctor; even if a doc thinks you should not stop taking a med they will tell you how best to stop if that is what you are determined to do.
Also, did he talk to the doc about changing meds? Possibly something else would work better for him. Or, as with many people, anxiety could be part of his diagnosis and he may need something for anxiety which is notorious for causing stomach problems.
I hope he's doing well. I stopped SSRI's cold turkey after 10 years. It was a mistake. I was sick for weeks, including too sick to work for a week. Nausea, diarrhea, headache, fatigue, head nosies, etc. It was pretty awful.