Holy shit! I've seen Utopia a few times through and never realized Philip's wife was murdered. I always thought it was natural causes, but you're right. :O I learn something new every time I watch this lol...
Btw, the driver wasn't killed because he saw their faces. Milner explained that the driver was the man who framed the CIA when The Network assassinated an Italian Prime Minister (the opening Italian news footage). The driver was also a journalist that Philip was leaking information to about the identity of Mr. Rabbit, not realizing he was a part of the Network, so they killed him because he knew too much.
Meanwhile, the Three Mile Island nuclear incident is real and did actually happen. I am pretty sure that all of the news audio/video clips that were used are real as well. They're likely all strung together out of context to fit the plot/narrative though. Either way, it is a bad ass way to strengthen the plot and keep it compelling by blending fiction and non-fiction together like that and the news clips are a cool way of showing how The Network rises to power and topples and embeds within the government decades before Season 1 takes place.