How do you pronounce
1. armistice
2. pitgtails

Can we assume the second one is a typo for "pigtails"?

Indeed.
Maybe I should expand.
Is it PIGtails or pigTAILS/
Is it ARE-mis-tis or are-MIS-tis?

PIG-tails
ARE-mis-tis

Of course, though, I irritate my daughter no end by pronouncing cigarettes like sig-er-ETS. Apparently the "correct" way is the stress the first syllable, at least that's what DD (dear daughter) says. So clearly I am not an authority on this.

ditto

The reason I ask is the "pigTAILS" pron is being used on a national commercial for Wendy's hamburgers. That's how the actress who's supposed to be Wendy says it, and I thought it odd.

The other is mis-said in a promo on the History Channel. It's strange that such a rendering is allowed there.