I used the exact same kit for my first brew. Like you, I also experienced a stuck fermentation which ultimately led to the beer having a strong diacetyl flavor (buttery, buttered popcorn).
It sounds like your initial conditions were favorable. Well aerated wort, good temperature, etc...
The blow off was just a minor set back. I would let it sit for a week, you should see a large drop in the gravity. If you don't, go get yourself some more yeast and pitch it (I use liquid and I do not trust the packets that come with kits). If you do use dry, make sure you hydrate it first.
If I recall, this recipe has a good amount of maltodextrin in it which is a non-fermentable sugar so don't be surprised if your final gravity is in the area of 1.014.
If I could go back and do my stout over again, I would let it sit in the primary for much longer and bulk age it in the secondary for at least 3 weeks. I rushed it and there is STILL diacetyl flavored stout available in my cellar. (though it is getting significantly better with age)