Of course I can answer those questions.

Ox-Body: Basically, Ysolda can endure a hit that would leave most beings writhing in agony or dead. I stated a normal Exalt's "Health Levels" within the charm for reference. She is simply more durable and hardy than someone without those charms. No further benefits.

Durability of Oak: No, she takes LESS damage from it, relative to the strength of her essence. At Essence 8 (Maximum Essence rating being 10) Ysolda would resist a significant portion of the damage, but not all.

Adamant Skin Technique: Correct. This technique can resist any and all damage from an incoming attack. You could drop a nuke on her head... if she uses this charm, she would be fine. However... with that flaw, if she makes any defensive maneuvers (running, jumping, etc) for two turns prior to using it, the charm fails and she takes the damage. Thus making this technique fairly tricky to use in combat. It's not a "use this THEN don't move"... it's a "Don't move so you can use this".

Seven Shadow Evasion: Currently, he motivation is assisting the realm of Necropoli. However, her grand motive is finding new and wondrous technology to assist the Solar Exalted in reclaiming their place in Creation. She's simply confused as to how to do this, and it's taking a back-seat while the more apparent goal is attainable. If a character shook her will to help others, then she could not use this technique. And once she affirms her goal to help the Solars, they would then have to shake her from THAT goal.

Yes, it can be used to dodge attacks that should even be undodgeable. Example: A character uses an acid rain technique that creates thousands of drops per minute per square yard. She would move with such speed and precision that she would actually move between each and every drop of acid... much like Agents in the Matrix can dodge automatic fire with ease. However. This does NOT work against surprise attacks unless combined with another charm that allows that.