I'll respond to both of you at the same time here.
First, on a brief note, I would not argue that prwtotokos is purely chronological. The firstborn was inheritly preeminent, receiving a double portion.
Second, loelaia, the example is a bit different than what we see in Colossians 1:15-16, for in the text in question, we are in a single sentence. Your example is rather different, for we see the comments of Matthew in narration, and then Satan is quoted directly.
I am aware of no example where change in gender ever occurs when there is a subject defined by an adjective-noun and then a substantival adjective (where the noun is elided) of a different gender is used to refer back to that same subject. I'm not saying there isn't one, but I'm not aware of it, so I don't well see how the argument being presented to the contrary can carry too much weight.
Further, we need only look to verse 20 to see ta panta used substantivally in a sense less than "all creation." This further leads to understanding the same in verse 16 in a way lesser than pashs ktisews.
Finally, I don't think that this at all takes away from the force of hOTI. Jesus is both first in time and the preeminent one of all creation because ta panta was created in him. Preeminent because of his role in it coming about, first in time because of his existing for it to be done.
Mondo