I got my easy paces from the training pace calculator in the runner's world website. It gave me a pace of 5:29min/km for easy runs which agrees with your advice that easy runs should be at least a minute slower than race pace.
Here's yesterday's 40min easy run:
1st km: 5:22 min/km
2nd km: 5:20
3rd km: 5:21
4th km: 5:17
5th km: 5:20
6th km: 5:11
7th km: 5:00
0.66 km: 4:45 min/km
Basically, i try to keep it on or below 5:29min/km; the closer to that pace the better (that's my mindset). I refuse to push too much during these runs to better prepare or condition my body for the hard sessions. This is my pace for the 1hr easy runs, 40min easy, and the 30min easy runs. .
My pace for the 1hr 30min long run is at 5:29-6:12min/km. I covered 16.30km in my last long run.
I just finished my 6x1min fartlek w/ 1min slow today:
Here are the paces for the fast ones (in order)
Regarding the heart rate monitor, right now I'm using the garmin forerunner 35. Although its paces are accurate, im not quite sure about it's built-in heart rate monitor. I know it wont be as accurate as the chest straps. Would that suffice though?
Kindly let me know what I should change and do next.
Have a pleasant day !