Shawn Sipos (Aaron Whitmore) is actually two years older than Rick Cosnett (Wes Maxfield) who plays his guardian and a professor at Whitmore College.
When Katherine inserts the needle into Dr. Maxfield's arm, she plunges straight down at a 90° angle, but this would simple blow through the vein. Needles must be inserted in the range of 15°-30°, closer to parallel with the direction of the vein.
When Amara wakes from 2000 years of immobilization. Silas mentions Qetsiyah as Tessa, she seems to know who that is but she only know her as Qetsiyah.
Silas says he keeps reinventing himself, "like Madonna." This pop culture reference would have happened while he was entombed.