That's very nice progress there on the 5k and 10k Cicero, I guess there's plenty to come of that half marathon if you just upped the mileage, pretty difficult to run good 800m and HM's simultaneosuly I'm guessing!!
I had a pretty good year until about September, ran a 37:31 10k in Bristol in May, and then 17:33 parkrun at the end of June.
I then had a great training block of about 10 weeks that should have taken me through the Swansea 10k and Cardiff Half in September/October (where I was looking at sub 36-min 10k and sub 80 Half based on training progression).
However, I got ill and then had a niggle two weeks before the 10k, which meant missing the 10k and not really training at all for a month before the Half so the result was an 82:56 which was not bad for a first half but not what I was after.
I then had a month or so of light training again when I got injured again (achilles) and am now in the midle of a 6 week running break as advised by physio and will start again in the new year. So pretty mixed all in all!
LSH I'd suggest alternating your tempos maybe between a true tempo run of 4 miles, for which 6:20/mile should be fine for you (based on your 5k pb) and maybe a longer tempo of 6/7 miles at marathon pace of around 6:40/mile. This could help with the endurance side of things.
Also maybe add a bit of volume to your interval sessions. Based on your 5k time, you should be looking at 37:30 for 10k which is around 6:00/mile. Good sessions might be gradually building from 3x1 Mile/ 5x1k at that pace until you can manage maybe 5/6 x 1 mile or 8x1k.
Also I would suggest 7:30 is slightly quick for your easy runs, slowing down to 7:45 would make a difference and make some of the sessions above more manageable.
Physio was convinced it isn't a stress fracture and that it is a pain in the tendon between the tibia and the adjoining muscle, caused by a lot of stiffness in the ankles from scar tissue (several sprained ankles) and lack of flexibilty. It sounded convincing!
Although if he says stress fracture he gets no repeat fees, and this way he thinks I need a few sessions to try and get rid of some scar tissue!