Corrected entry: The Stargate above the Wraith homeworld seems to float in space with no DHD, so where is the gate drawing power from whenever someone dials the gate?
Corrected entry: It is stated throughout the series that the stargate dematerializes anything which passes through the event horizon. How then are people able to step into the gate? Their legs dematerializes immediately after passing the event horizon (and the stargate doesn't transmit the leg until the whole body is dematerialized), so that leg couldn't support their body when they step. They would literally fall into the stargate.
Correction: The Stargates use technology that is so advanced it's almost magic. Since people do walk through them and pull things through them, the Ancients clearly designed them to make it possible. After all, how useful would they be if you couldn't take anything through them but what you are carrying?
Corrected entry: The wraiths' darts are using a transporter-like beam to collect people to feed on them. As it turns out, this device somehow stores information about the collected humans, without actually transporting the human aboard. Later, using this information, it is capable to reconstruct the human which was "transported" to the dart. Now, if it is possible, why would the wraith bother with those elaborate "harvesting-runs"? If they are capable to construct a whole human body based on some kind of stored information, they would surely be able to construct several human bodies based on the same information. This way they wouldn't have to hibernate themselves for hundreds of years (the primary reason of the hibernation is the depletion of their "feeding grounds" - this is one of the reasons why they such desperately wish to know Earth's location).
Correction: You have misunderstood the concept. The darts appear to work in the same way as the Star Trek transporters, in that you are momentarily stored in a buffer and then re-integrated. But with the darts, the people are stored longer, and reintegrated at a later date to be used as food. Once the human has left the buffer and been reintegrated, there is nothing left in the buffer to 'clone' or 'create' a new one.
Corrected entry: Dr. Weir says that the Atlantis gate is the only one that can dial back to the Milky Way from Pegasus galaxy. SG-1 has already confirmed that any stargate can travel intergalactically if it has the power. That's what the 8th chevron does. You need a Naquadah generator or Zero Point Module to provide the extra power though.
Correction: This is answered in episode #108, all the Pegasus Stargates are missing a crystal except for the Atlantis gate, this crystal allows it to dial to other galaxies.
Correction: You don't need power to be dialed into, and the portable dhd's on the jumpers power it for dialing out.