I guess someone else can comment more on the remaining aspects of your case, especially how the styloids might affect the voice etc.
But as for chiros… I’d say, avoiding any sort of neck manipulation with the styloids compressing the IJVs might be the best (though I’m not a doctor so my advice isn’t necessarily perfect). Think of that like this: any forceful rapid motion beyond the range the body has, means some soft tissue has to give up. When it’s stretched slowly, multiple times, over the time the tissue remodels itself (My Favourite List of Research/Educational Resources). But when the rapid, sudden manipulation is performed pushing some joint beyond the range, it means something may break. And that could be anything from microtears in tendons, membranes, ligaments, or in your case the styloid processes might completely crush the veins. Not trying to say it will happen, but it’s very heartbreaking to read all the stories on various patient support groups where people develop neck instabilities after chiro manipulations… Neck instability is something I don’t wish anyone to acquire.
Also read this:
Ah, I missed this one:
Perhaps. But not necessarily.
I’ve heard some success stories of people getting help from atlas orthogonal chiropractors.