Question: Sam says a stargate's range is roughly 300,000 light years, yet, in the movie, Earth connects to Abydos "on The Other Side of the known universe." Why the discrepancy?
Answer: For an out-of-universe explanation (that is to say in real life), when the TV series was created, the idea was there were thousands of other Stargates out there that the original film didn't account for, so they just wanted to have everything happen in the Milky Way galaxy. In s01e01, Daniel finds the star charts on Abydos and they (the writers) had to explain why the Stargate on Earth didn't connect to any other Stargate except for the one on Abydos. In-universe, this is because of stellar drift but Abydos was so close that there wasn't enough stellar drift to affect the connection (meaning it is in fact located in the Milky Way). In the film "Abydos" was said to be located in the Kaliam galaxy and an in-universe explanation (though never stated outright) is they initially got their calculation wrong when determining where the planet was. Later in the series, Vala makes a reference to the Kaliam galaxy as a nod to the original film.
Question: Why did O'Neill shoot Reese at the end of the episode?
Answer: Because Reese was controlling the replicators, or at least still linked to them, and he saw shooting her as the only way to stop the replicators. However, Daniel suggests that Reese deactivated the replicators prior to being fatally shot, so the audience is left to wonder who was right.
Answer: In Tangent, a captured Goa'uld Death Glider was retrofitted into the X-301. Unbeknownst to the SGC, it contained a recall device that would automatically make it return to Apophis home base. Teal'c and O'Neill were testing it when the device activated sending them into deep space where they nearly died. O'Neill wants to make sure the cargo ship doesn't have something similar.
Grumpy Scot