break the task down into very small sections... and give verbal reminders,( or visual reminders? ) using his name..
sand timer?
bribery and corruption? if you write 2 sentences before play you can have a go with the... ?
a maarble in the jar (etc) for everything he completes.
remove the requirement for him to write the date/title, but he gets on with one specific thing you want.
have you tried repeaating the instructions to him using his name, so he knows it applies to him too?
has he had hearing test?
have him do the work on the computer/ipad
can he do it with objects and you record with photo?
until he has been assessed and you know where the problem lies, it is difficult to know what to do to help.
somewhere along the path of listening to the instructions, understanding them, remembering them, concentrating long enough to do them, getting organised enough to have pencil and paper, using his fingers to write, knowing what to write, getting the message from his brain to his hands, there is problem.. the difficult bit is working out what it is.
do you need to draw the lines on the paper so he knows where to write? a dot where to start?
can he record what he wants to say and then someone writes it/ he writes it?