Armor 0.
Cut Away is an effect that expires during the Closing Phase that is still on the Mechanical Rider. When the Spell was cast, all the requirements were present.
Self Loathing doesn't generate a Strike, it just generates a Damage Flip at with the Weapon.
And since Chimeric Assault doesn't do any damage unless he's performing a Strike, it would be better to choose his Shillelagh.
No you may not.
A model may NOT intentionally perform any Action or Ability that would kill or sacrifice itself unless the ability used allowed it.
Which is why some of Leveticus' Actions state that he MAY kill himself with specific actions.
This was ruled ages ago and many times since.
Overpower automatically Triggers and you are only allowed one Trigger per Duel.
The Overpower is "mandatory" aka: MUST. And it will be the only Trigger that may be used. You may not Surge with Biting Chill.