Welcome to the forum always glad to have new members!
1. Why a 16" Barrel?
2. Any stock with the 4.275" screw spacing for a Savage model 10, 11, 12, 14, or 16 will fit it.
3. No help from me with that I like blind mags.
4. I've worked on one of the older triggers and with some patience and the right instructions it turned out fine. If you upgrade there are a number of triggers available. I've heard really good things about the one from Sharp Shooters Supply.
5. How far will a 16" .223 Wylde reach? Might not have any need for a 20 MOA base.