McKay said they had been exposed to 327 mSv of radiation at that point. An acute whole body dose of 250 mSv results in the onset of hematopoietic syndrome, which is the destruction of the body's ability to make blood cells (hematopoiesis). This can lead to infection due to lack of white blood cells, bleeding due to lack of platelets and anemia, which causes weakness, confusion, shortness of breath. Over the course of the episode, they're exposed for many hours yet experience none of these symptoms.
The doctor uses a cheap Chinese 'Optivisor' instead of precision surgical enlargement optics.
Since they know the Wraith darts are optimized for gate travel, it makes no sense not to put some kind of heavy weapon or obstruction directly in front of the gate during this operation. It would be the simplest thing and easily prevent surprise air attacks.