My bf’s panic attacks are ruining his life

TLDR: Here are my questions: 1. Are fainting and vomitting during a panic attack common? 2. Is it normal for panic attacks to last multiple days? 3. How can I help my partner during an episode?

Long, sad story ensues: My partner (42M) of 9.5 years gradually started having panic attacks roughly 3 years ago- for no specific reason. At first, they just made him really nervous and uncomfortable for like 5/6 hours. Then they got gradually worse and more frequent; and he started having to spend like a whole day in a dark room. Then the panic attacks started happening more often and lasting for multiple days.

Over the 8-9 months, he started full-on fainting-- like in the middle of an activity. I had to pick him up from some hotel staff earlier this week because he fainted and they wanted to keep him in a room until he called 911. They let him leave because I promised to take care of him. I've personally witnessed the fainting twice in the last 6 months. He gets very pale and clammy and he falls on the ground. It's scary.

He's currently on day 4 of a severe episode, and he just vomited. Wtf?

He's on medication (Paxil every day plus some tranquilizer I don't know the name of as needed) and he regularly sees a prescriber and therapist. Because of the vomiting just now, I asked to join his next doctor's appointment and he flipped out on me. The reason I want to come is that I think these doctors don't understand how severe his symptoms are because he's very professionally successful and functional in all of the outward-facing ways. (He always underplays/tries to hide his symptoms pretty well.) Also, I suspect his heart is part of it. (He has been tested and they said he just has a mild arythmia.)

Thanks for your help. I love my partner so much.