Love the k by k analysis that a 5k produces. I have similar analysis to what you've done. Not sure about the training for the uphill ks but certainly hill work seems sensible - bike would be the other thing but you generally do plenty of that and it makes you strong but not necessarily fast.
The 5k race really does lend itself to a km by km analysis, esp when done over the same course. It is not surprising that the 4th km is the hardest, and the training recommendations for increasing the speed endurance are fairly straightforward, at least in principle. More hillwork is definitely on the agenda. I am not doing so much biking these days because I am having trouble stirring myself at the 5.15am alarm call. We are still on daylight saving here and it is very very dark in the morning. But no real excuses so will need to get out again more regularly.
In other news, have signed up for the Paris Ekiden marathon relay in 4 weeks time. Team of six from work and I am running the last 7.2km leg (the first legs are 5-10-5-10-5k each). Should be fun.
Relay sounds fun. Those Ekiden ones are fairly famous I think.