[One had a doctor tell them "This drug cures everything"]

I wouldn't say it cures things, it may stop the cycle of something and if you're lucky that thing goes away, or it may be stopped for awhile.

It's also used for autoimmune conditions.

Is he on a 5 day dose pack or a little bit longer that?

I had a bad respiratory infection last year and had the 5 day dose pack.
Dh, my brother , his daughter & her dh all ended up needing a dose pack to fully get over the lingering respiratory /flu symptoms.