If our power grows enough, would we be able to forge a new afterlife destination for our followers?

It feels to me like being benevolent would likely be the safer and more rewarding long-term strategy, while taking sacrifices and being a bit more bloodthirsty would be a high-risk high-reward path that may have a weaker future ahead of it. Easier to grow the numbers of the faithful when you aren't killing them / forcing them to kill, after all.

With this in mind, I think I'm officially casting my vote for striving to be a benevolent deity.

Also, correct me if I'm wrong, but the way you were describing the world it sounds like it's a modern day parallel?