Wow, Barb, that sounds really bad. Sounds like this kitty has developed a fear-related mean streak.

I wonder if one of those cat-feramone releasing wall mounted dispenser things would help. We have used one called Felliway with good success.

Definitely sounds like a serious behavioural issue.

Hard to say if neutering will change his attitude, and probably not right away.

I would make sure that James is the one to put him in the carrier, and also is the one to carry him in and out of the vet. chances are if he thinks you had anything to do with that coming vet visit, he will hold it against you.

Someone who has a lot of experience with a wide variety of cats is Beth Bach. You might want to tag her in this story, maybe she might have some ideas.