10k/HM improving training

Hi, looking for some advice on improving my training for 10k/hm's over the next 12 months. I started running last August after stopping smoking. Ran first 10 k last November in 50.47. Then first HM in march this year in 1hr 58m. Trained and ran a marathon in October in 4hr 7m. I am looking to structure my training more for the shorter distances over the next 12 months with the possibility of doing another marathon in autumn. I am currently doing around 30 miles per week but have to juggle this with a shift pattern of days/nights-12hr shifts. I have a 10k race this Sunday and a HM on 3rd nov which I intend on using as my bench marks for these distances. I am aiming for 47mins for the 10 k and 1hr50 for the HM. Targets for the next 12 months would be 42m 10k and 1.40 HM. With a marathon aim of 3.50 if I enter one. Just after any advice on best way to structure training, should I train for 1 distance etc Cheers, and apologies for the long post Pete