Answer to "Can superglue be used instead of soldering, and would it be safe?"no it's definitely not as because it will damage the solder points
Answer to "What is causing these lines on my iPod's screen?"In my opinion it would be better to clean the display terminal this would fix the problem rather than replacing the logic board . I faced similar problem a month ago and I was successful when I cleaned the display terminal with a light solvent(VCR head cleaner)
Answer to "Can I use this to solder a logic board on my iPhone?"Yes,but we have to be very careful about the other components and wires on the circuit board because this iron emits a lot of heat .While soldering a particular component we have to be quite careful about the wires on the circuit board, otherwise it may melt away.Keeping in concern about all these this soldering iron is a must for every repairs and for every electronics repair enthusiast.