Yang shows that she will always consider Summer to be her true mother; not even giving Raven a thought.
The writers confirmed that Hazel was purposely going kamikaze on Salem, to buy everyone time to escape.
The amount of Dust he injected into his body was a fatal dose anyway.
Salem believes Emerald took the lamp, demanding she stole it. A nod to Emerald being inspired by Aladdin.
The writers intentionally invoked the Salem Witch Trials by making it look like she was burning at the stake; while in Hazel's bear hug.
Salem's regeneration is much more gruesome that before she jumped into the Grimm Pool centuries ago. All her injuries now regenerate in black goo with a red glow. Additionally Salem seems immune to most pain, not even reacting to her chest exploding except a recoil and her face being bashed in beyond annoyance. Though when Salemsl's face regenerated, she did adjust her jaw; suggesting some bones don't always set right. The only time she reacts, is being set on fire; screaming. Though this may just be Salem's immune rage.