The battle reports look fun, but I can't help but notice you are doing close combat slightly wrong.
When your Genestealers attack his Thousand Suns and Ahriman, you need to pick how many attacks you are directing the attacks against the
IC or against the squad. Since they are different units for the purposes of resolving assault.
Likewise wounds directed at the squad cannot be allocated to Ahriman- although they could be allocated to the Aspiring Sorcerer, since he is still in the squad.
EDIT: Ahriman can cast Gift of Chaos in combat! you should have let your opponent know that Ahriman could have been turning up to 3 genestealers a turn into chaos spawn

!