You have remove his gadgets which is great. May I ask about TV or computer? Is he still watching it or spending some time on his computer after finishing homework, even for peaceful things such as watching family photos? I ask because I read "deadly wandering" and other books (iMindm rating children in a digital age, ...) on the effects of screens on a child's brain and ALL highlights how excitable children become , and other effects.
Could you go out on a walk after dinner. Leave your DH tidying the kitchen, grab a coat and just go for a walk for 30 min, looking at the houses, dogs, ....
Another suggestions would be to go at the library, and take the maximum amount of books allowed on your card, even if you have hundreds of books at home, facts and science books, fiction, jokes, .... and sit all together for 30 min reading in the lounge, then teeth brushing and to bed.
Last, can you add some sport? DS2 is 11 and in squads swimming. He goes swimming for an hour either mornings before school (at 7am in the water so up at 6.10) or after school and by 8.30 is shattered and the second his head touches the pillow, he is already sleeping.
Very very last, diet. Eating kiwis in the evening could help according to this medical study. No harm in trying
"In summary, consumption of 2 kiwifruit nightly 1 hour before bedtime for 4 weeks resulted in improved sleep onset, duration, and efficiency in adults with self-reported sleep disturbances. The results of this study suggest that further research into the sleep-promoting mechanisms of kiwifruit may be warranted.
" Full study here apjcn.nhri.org.tw/server/APJCN/20/2/169.pdf . Almonds ad raspberries are almost high in melatonin so instead of biscuits after school, a bowl of each might help. Goji berries have the highest amount however they are not easily found .