Najis things is unlawful to consume. However, you did not know that the cake is najis, so you have not committed a sin.
Based on compulsory precaution, one should not desert a believer for more than three days, even if the latter was wrongful to him. It is sufficient to satisfy this obligation by greeting him (e.g. saying 'salam alaykum'). If the other party insisted on the abandonment, he will become the deserter. This prohibition has three exceptions: First: if the desertion was to forbid the wrong. Second: if the desertion would lead to a benefit that the Sharia recommends, like - for example - if desertion leads to paying attention towards a truth that could remain hidden without such desertion, or similar cases. Third: if the reestablishing the relationship would lead to demeaning oneself. One should be careful in not confusing arrogance and anger with self-demeaning.
It is not permissible to use the item without the owner’s approval. The stealer is obligated to seek the owner’s approval, or he must return the item to owner even if this is done without the later knowing it was stolen in the first place.
If the divorce by the Sunni judge was based on the religious laws of the sect of the husband, the divorce is correct, even if it is not registered in a legal way. She can remarry after observing the waiting period (the iddah).