Don't think that a blocked vent would cause that. From what I hear, a blocked vent will potentially cause a trap to be siphoned dry, but not affect the drain much. A line could be clogged where a vent comes off, and that could cause a trap to be sucked dry giving you the sewer gas smells, but it still sounds like to me you have an obstruction in your drain line somewhere. If he used a toilet auger, that only goes down about maybe 4-5', if that. If he used a power auger and did it through a toilet, I don't think that works too well and could damage the toilet. Those can be quite long (say maybe 100'). One of the pros will probably have some thoughts on this as well. I guess you could pull the toilet and power auger from there.