The Actix unsafe code has long since been resolved. There are very few instances of it, and each are small, specific, easy to reason about, and wholly internal. I'd guess the risk is about on par with—or safer than—VM runtime languages written in C/++.

Far as 1.0 in Rust, the predominant culture is to treat "0.X.x" releases roughly equivalent to a "1.x" semantic. I have run into very few issues of API breaking changes in "0.X.x" libraries, and even those are basically handed to you thanks to Rust's robust compile-time checks.

Of course your mileage may vary, but I've had a way worse time with even well-established breaks in Ruby, Python, and Go libraries. I understand your risk aversion; I am similar. But I've found Rust to be an absolute delight for stability. The shaky ground of the first few years has largely given way to impressive robustness over the last few.

I strongly urge you to consider Rust if it matches your needs. You may be quite pleased!