1. The idea of DNA as a durable data storage device is interesting. You can encode digital data as 0/1 purine/pyrimidine (or other schemes). And it's tiny, easily compacted, and can store unbelievably large quantities of data in a small space. The major drawbacks are the fragility of the molecule itself, and the difficulty with read/write functions. I've seen people talk about deep freezing huge archives of data on DNA, but practically, I think the closest we've seen is the Seed Bank which stores genetic samples of species from all over the world in an effort to protect against extinction.

2. Junk DNA is a terrible term. Worse is the sci-fi around what it actually is. DNA is a chemical, first and foremost, and it is governed by the rules of biochemistry. It gets copied, cut/pasted, inserted, swapped (cross-over) all fairly routinely. Sexual reproduction is based on this. Viruses frequently insert themselves as well. So, we get copies of genes, sometimes copies of whole chromosomes. We get genes that exist, but mutation renders them non-function. We get viral "fossils." We get mutations from all sorts of stuff in the environment. And if it doesn't kill the critter and the cells makes copies, all of that information gets copied and forwarded to the next generation, on and on, even as new species evolve.

Humans carry several prominent genetic fossils. One is the remnant of a virus that occurred for something like 15 million years and infected just about every mammal species on the planet. We all have that one. We also have a non-functional pathway to make Vitamin C. Over 10 million years ago, our monkey ancestors could make it, but because they were eating fruit, a mutation that broke that enzyme didn't kill off the ancestor. They lived, reproduced, and passed on that mutation as they evolved down to us. Our ancestors used to be able to break down uric acid too. We lost the ability and now get gout if we eat too much, but we still have the fossil of the non-functional pathway. I haven't even touched on the epigentic stuff, but this isn't "junk."

But as you say, there's a ton of potential with this stuff and it is fun to think about and explore some ideas, even if it's just through good sci-fi.