Hello @MostlyReallyMatt !!
Good to have you with us.
SWEEEET
If you’re cutting the strip into 6 shorter strips you may get away with powering it from one end just fine.
Amps
I remember the 144leds/M strips were 5A per meter so this math feels about right.
Some good news is that it’s only 30A if your rocking full brightness white on every single LED.
30A of batteries feels like a lot to carry but if you can write code that ensures… maaaaaaybe a little less that that you won’t need an Arabian Camel following you around to carry your wine-skins full of lithium. 
You’re writing some code that emulates fire so I claim that many of the LEDs in your gird are going to be off anyway to form the shape of the flame. 
If there is a battery solution to this I’ll leave it to the CE to make a product recommendation since they will be familiar with the stock and your options.
AAs have 2 AmpHours right? Battery backpack? … do it? 
Design
Bit of a trade off here. I believe that 6 separate strips will be easier to power with batteries since there unique draw will be smaller. This will make it easier to debug since you can treat each strip as it’s own machine.
In exchange you’ll be running six Data Pins from the ESP8266 which will take a little more code because you’re trying to print a coherent image. That’s a trade off I would take but that’s a personal preference.
How flexy does this need to be?
If you don’t need these to flap in the wind would you consider working with something like this?
Lastly, @Murray125532 had some cool thoughts for me when I asked a similar question last year.
Pix 
