They are a smaller diameter than 209's. Toss em.
Yep. Be hard pressed to find shot shells that accepted 157 size primers.
I've read of guys using an "appropriate" straw to act as a shim/bushing, but...............
I wouldn't mess with them for shotshells or muzzle loader designed for 209 size short of an apocalypse/EOTWAWKI.
The only surefire way to make them "safe" to dispose is by expending them. I might be tempted to throw them in the bonfire.