Surface thoughts - This is okay. A lot of it is just sadness and anxiety as well as a sort of emptiness. He hides it well on his face but it's always there just under the surface.

Deeper memories/issues - At this point in his canon...no. He doesn't view what was done to him to make him a werewolf as an injustice he suffered any longer. About the only thing he has going on right now is deep regret that he's not there to lead his pack.

Invisibility - Sure but honestly he'd probably not prefer it.

Forget Justice - This would definitely require discussion between us just because Sandalio would likely react poorly to it if he found out this had taken place.

Possess your character - I'm going to say no just because things could go really badly since Justice doesn't have the years of experience that Sandalio does with handling his werewolf abilities.

Mind fuckery - This is another thing we can discuss in advance should it ever come up!