Can a person be saved if they believe Satan is their scapegoat? Seventh Day Adventists teach this. They are careful to say that Satan is in no way a sin-bearer, but their prophet Ellen White wrote about this in The Great Controversy (Chapter 18, The Sanctuary). If a person reads Ellen White and believes Satan bears the final penalty for their sin, are they believing in a false Jesus who didn't complete their atonement?
That is a conclusion one might make, but that is a conclusion Seventh-day Adventists reject. They state: “Satan makes no atonement for our sins. But Satan will ultimately have to bear the retributive punishment for his responsibility in the sins of all men, both righteous and wicked. Seventh-day Adventists, therefore, repudiate in toto [their emphasis] any idea, suggestion, or implication that Satan is in any sense or degree our sin bearer. That thought is abhorrent to us, and appallingly sacrilegious. Such a concept is a dreadful disparagement of the efficacy of Christ and His salvation, and vitiates the whole glorious provision of salvation solely through our Savior.” (Questions on Doctrine, page 400).
Without question, Seventh-day Adventist teaching fails to see the scapegoat on the great Day of Atonement (Leviticus 16) typifying the substitutionary work of Jesus Christ.
The larger problem is that Seventh-day Adventism fails to distinguish clearly between law and gospel. Ellen White, one of that church’s early leaders that you cited, wrote: “In the Law is embodied the same principle as in the Gospel.” The message of the law and the message of the gospel are in fact opposites. The law reveals our sin and our need for a Savior; the gospel shows us our Savior, Jesus. Jesus’ loud cry on the cross, “It is finished” (John 19:30), reveals that the Lord successfully completed his soul-saving mission. His triumphant resurrection from the dead guarantees it (Romans 4:25).