Where are you at in this country of ours, mate? Perhaps I could help in person. One thing I know how to do is train recruits, well it was Army but the fly boys can't be too different, except wussier with better food
Your cardio training is too heavy, 160-180bpm is no longer aerobic - that is, you're not developing your body's ability to draw oxygen through it better. Aim at 130-150 instead, at least until you can hit 2.4km in under 12'00". Yes it's counterintuitive, but going less hard actually builds you up faster fitness-wise.
If you're using a treadmill in a gym, have a look for the button that says "fit test". It asks your weight and age, then when you start gives you a 1'00" warmup, then the tread tilts to 5 degrees and you go for 4'00", based on your heart rate then it figures out your VO2 max - that is, the maximum rate that oxygen can be got through your system by your body.
Then come back, tell me your VO2 max and how many situps, pushups, heaves and bodyweight squats you can do in one go, and I'll write you up a 12 week programme to build you up enough to breeze through the physical training.