Good, strong lyric, for the most part. I look forward to hearing it once it's recorded.
I do agree about the "ain't"--and the "don't" you mentioned, as well. There are ways to "fix" those (if they do need fixing).
In "The days we get ain't very long", of course, you can use "aren't".
The line "Ain't no place to run for cover" could use "There's no place...." instead, perhaps.
Then for "It don't light the way", "It can't light the way" might work. ?
And maybe "Don't matter how we try to fly" could become "No matter how we try to fly."
Aside from those bits, I really, really like the way the words flow. I would list all the phrases that I find delightful, but there are too many of them. I would be including most of the song. I think verse 3 is my ultimate favorite of the whole thing. And I also like the topic a lot. It's almost totally my kind of thing. My one nit for the lyric as a whole is the darkness of it. I'm really not into dark, but I think I'm maybe in the minority there. Dark themes seem to the usual these days...all the old movie themes and TV shows coming back, but so much darker than they used to be.
Anyway, I personally would prefer a more uplifting, optimistic treatment of the theme, but that's just me. I still like it a lot, and the way the words work together is just, really, great.
Vicki