Is it permissible to resort to soothsayers to find out if the woman one intends to propose to is bewitched, or should he await Allah's decree?

Going to soothsayers, diviners, and sorcerers is a grave evil that contradicts the creed of Tawhid (definition) (monotheism). A person's share in this world is written and predetermined, and no one can change it. One should busy oneself with supplicating Allah and humbly imploring Him, and consistently performing obligatory and supererogatory acts of worship and seeking forgiveness, for Allah, the Almighty, says: "And said, 'Ask forgiveness of your Lord. Indeed, He is ever Forgiving. He will send [rain from] the sky upon you in [copious] showers And give you increase in wealth and children and provide for you gardens and provide for you rivers.'" What you are feeling is not possession or magic, but rather whisperings from Satan, so seek refuge with Allah from him.