If you purged after only 15 minutes, that would not be enough time for your stomach to absorb the dose, so that's likely why it didn't work.  You may want to filter before reducing, so the filterable material is less concentrated.  If you filter after reducing, the drink is more concentrated, so any drop that gets left behind will contain more actives.

In my experience, nausea is less if the tea is less.  I want to get it down to half a shot glass, easily enough for one sip.  But that's with a few grams of mimosa.  I've never tried chacruna.