If you ingested black widow venom, would it affect you?

Probably not. As the other answer said, venom needs to get into the blood stream. Things in your stomach can and do get into the blood stream (like water). But venom is made of complex biological molecules. The acid in your stomach attacks things like that and tries to break them down. So the stomach acid would probably alter the venom to something less dangerous before you had time to absorb it into your blood stream. More simple molecules, like poisons (cyanide, lead, etc) are usually more sturdy molecules and can survive the acidic environment of the stomach, and are thus very dangerous to eat. However, I would not try to eat any venom, since it is your life you would be playing with. And things like ulcers or low stomach acidity can make it much easier for things to make it into your blood stream.