my wife who does know much about Islam has threatened to divorce me if I convert. Your wife is very understandable. Any sane person with decent knowledge of Traditional Islam wont wanna have anything to do with it. It is dangerous and even more so to women. So be understanding of your wife. As for your shahada question, submitting to God is a mental state. It has nothing to do with signing up to be a Muslim at a mosque and receiving a membership certificate to prove your Muslimness.