Gavin, thanks for the explanations.
Regarding the easy runs, if I run by pace and add 60s on top of the 10k race pace, I find myself running in Z4(lactate threshold > 150bpm). Hopefully, during training cycles, the HR will drop while keeping the same paces. My 10k aim is ultimatelly sub 40m, but I understand that it's a long way 'till then.
Regarding the 5k run, I was asking because I saw on some training programs(sub 40min 10k for example) that "you should not run faster than 19:10". So I was wondering, based on the time trial results, what limits shoud I run within.
I also cycle(road & mtn bike) and do some strength trainig at home(with dumbells). When do you think it's ok to add these in the program?