So sorry that after the hunt for someone to help and pushing for surgery that it’s not been enough to help with your husband’s symptoms…
I agree with @Isaiah_40_31 about the other anatomy which could be causing compressions, and that stenting should maybe be the last resort. If you have copies of your husband’s scans, & if he can get new imaging done otherwise some members have sent their images to Kjetil Larsen at MSK Neurology, here’s a link:
Home - MSK Neurology
He seems to spot things in scans which other radiologists miss!
The doctor you saw for your husband’s surgery has authored a research paper although we’d not heard of anyone having surgery with him. There’s one other on our list but don’t know much about them so not sure if they’d be any help, or you might have already heard of them:
Dr. Thierry Ladner, Hospital CHIREC, https://www.doctoranytime.be/d/stomatologue/ladner-thierry?utm_source=gmb&utm_medium=organic&utm_campaign=profile
Hopefully others will chip in as well, but you mention pain at the back of the skull; if there is compression of the IJVs, other veins can swell and take over (collateral veins), so that could perhaps be causing problems and pain. Other members have had issues with the transverse sinuses in the brain
Here’s a link to one discussion where @KoolDude has talked about compressions of the IJVs, and transverse sinus issues, which might be interesting for you.
I hope that your husband is able to find some treatment to help, thinking of you both 