I think it's just best to leave Gowther's emotion restored key as unknown, especially when it comes to striking strength.
Has a power level of 35,400 which is in between Unsealed Base Meliodas and Critical Over Galand
We've agreed to, for the most part, not simply scale combat classes when the sub-categories are unknown. There's exceptions of course (like Ludoshel and Mael), but Gowther very rarely uses his magic and physical abilities for direct or physical purposes, and is
most likely just magic.
Has enough magic power to assist the original Gowther in casting his forbidden spell
This isn't really anything AP worthy.
A combined attack from him and Post-Training King destroyed a weakened Base Chandler's magical wall at night in one shot
It's unknown how much Gowther contributed, or even if he
contributed to the power of the attack itself rather than just damaging Chandler's spirit, especially when King alone could
one-shot him with Form One. Plus, even if he did, Gowther's magic can
potentially exceed Destroyer-type.