First I would not use a generic formula to determine your max heart rate. Ideally you could do a Vo2Max test and get that but your next best way is to run a couple of races to determine where you max HR is. Since you are already seeing a spike as you go up a hill you can use that to figure out a reasonable Max HR.
Find a hill that is about 300 meters long. Sprint up the hill and slow jog back down for recovery. Do this at least 6 times. You will be able to find your Max heart rate or get fairly close to it.
The question or statement
I'm not able to run slower
If you are jogging to the point of walking then try walk jogging. How fast are you running when you can't run slower?
Here are a couple of options for your 14k runs. (And by the way you don't always have to run 14k)
4k warmup, 2k at 1/2 marathon pace, 2k at 10k pace, 2k at 5k pace, 4k cool down.
Make sure you are not doing this everyday. You should mix this up with recovery runs then hard work outs. No more than 2 hard workouts per week and I would incorporate one long slow run on the weekend.
In addition to the above you should incorporate Hill repeats and Speed training.
It will take some time, maybe more than year depending on your weekly kilometers.