Never dump a batch after tasting it right after the bottling.
At 8% ABV and probably fermented at around 25°C it's gonna taste like **** for a long time. For anything belgian (excluding wits) 6mo is the minimum aging required.
I've made a couple of Brewferm kits, and I can say that they are top quality, but need to be aged a lot.
Also, leave it to ferment for 2-3 weeks, not the 7 days recommended on the package.
I can guess that the off flavors were green apples and yeast.