You can use an acetylene tip, but propane-specific tips will retain the flame better. I modified an acetylene tip by making a very small countersink around the hole, and it works much better than it did previously.
I use a flashback protector on the propane side only. No need for one on the oxygen contentrator.
A two-stage regulator is the way you'll want to go.
And yes, bronze will be plenty strong so long as you get good penetration with a nice internal fillet and goo throat depth on the external fillet.