Growing your faith is getting saved in one sense of how "save" is discussed in Scripture. Again, we were saved - we're being saved - we will be saved.
So, yes you are changing the language. The moment you change "salvation" to "sanctification" you've changed the language. If we do not change the language
clearly stated in Phil2:12, then we do work with God to accomplish salvation. Even if we "work out" our salvation, is this really any different?
Yes, the 2Pet verses are speaking of the same thing and they are also describing what we do in Christ in Spirit with God working in us. As are other Scriptures describing the same thing. And here in Phil2 Paul very clearly describes this process as accomplishing our SALVATION [which we've been given according to Paul elsewhere] together with God providing the capacity/energizing (energeō is the Greek verb).
Bauer-Danker, Greek-English Lexicon of the NT (BDAG)
[BDAG] κατεργάζομαι (katergazomai)
1. to bring about a result by doing someth., achieve, accomplish, do τὶ someth.
From Merriam-Webster:
work out
2 of 2
verb
worked out; working out; works out
transitive verb
1a: to bring about by labor and exertion
work out your own salvation—Philippians 2:12 (King James Version)
b
: to solve (something, such as a problem) by a process of reasoning or calculation
c
: to devise, arrange, or achieve by resolving difficulties
after many years of wrangling,
worked out a definite agreement—A. A. Butkus
d
: develop
the final situation is not
worked out with psychological profundity—Leslie Rees
2
: to discharge (a debt) by labor
3
: to exhaust (something, such as a mine) 1by working
FWIW, MW is the first dictionary I landed on.