If you are unwilling to run easy then there is a limit to how much improvement you can make, however you are nearly there already on the sub-20.
I would just say try and increase the distance of the saturday gradually towards 15-16k. Same for the mid paced runs towards 8k. For the fast 5k maybe split it into 1k/1mile intervals at 4min/km pace with 90 seconds rest between intervals.
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.