Greetings Rebel,
Although I do not agree with many of the SDA teachings, including the two that you mention in your OP, I do believe that the soul is mortal. Perhaps a few Scriptures without getting involved in a discussion here on this topic:
 Genesis 2:7 (KJV): And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul. 
Genesis 2:17 (KJV): But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. 
Genesis 3:19 (KJV): In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return. 
Daniel 12:2 (KJV):And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. 
Acts 2:31-32 (KJV): 31 He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. 32 This Jesus hath God raised up, whereof we all are witnesses. 
I personally believe that it is an important subject, and worthy of careful consideration.
Kind regards
Trevor