Is it permissible to swear by (Allah "The Living")?
Yes, it is permissible because "The Living" is one of Allah`s Attributes.
Is Zakah (obligatory charity) obligatory on indebted merchant?
Debt doesn`t abrogate the dueness of Zakah, thus a debtor who has money, articles of merchandise, or other Zakah funds at his disposal should pay their Zakah.
Is it incumbent on the fiancée to obey her fiancé?
When the woman settles in her husband`s house, it is incumbent on him to provide for her and it is incumbent on her to obey him. Before that, and if the marriage contract had been concluded, then she is lawfully his wife and thus she should abide by custom in treating him, but if the marriage contract hadn`t been concluded, then she should treat him as a non-Mahram (Marriageable).
Am I Permitted to Use Ill-gotten Money given to me from Sorcerer's Sons during during my Mother's condolence?
You are permitted to use this money if you were ascertain that the majority of his lawful money surpasses the unlawful one. And Allah Knows Best.