Malika, even if J would be most neurotypical child in the planet, at age of six, his understanding of time is limited. While you have that basic structure of your day organized in your head, know how long J can for example play before school at home or when you have to leave to be in time for some activity, J doesn't. He is still young enough to live in moment. And being a bit different, it will likely take him bit longer and more work to get that understanding. Shoot, it is not untypical with adults with ADHD to have lots of difficulties with that. So from J's point of view, you are just always 'bossying him around for no reason' by telling to hurry, that you have to leave now, that J can't do this or that, because you would be late or dinner is almost ready.
Having that schedule for J to see would help him to understand better the structure of your day. To see, that for example this day you eat right after he comes from school and after that you go to activity X and he can't start an elaborate play after you have eaten and expect to be able to finish before you have to leave. It can help him understand the time better and organize his own thinking and help him learn time management skills. It can also take unnecessary tension out of your life. Also some things you have told about J suggest that some of his difficult behaviours can be partly caused by anxiety. One big help for anxiety is to know, what happens next. And even though you know and likely also tell J, it doesn't mean he does know. Schedule he can see would help in that. MWM is right that there is not schedule in real world and that is why everyone has to be able to create their own and keep it. if you are not able to keep schedules you better be darn good in what you do, to be able to feed yourself.
As buddy and others have already written using it smartly can also help you teach J to make choices, lessen conflicts and help him be more flexible with schedule changes.
If J would think pictures too childish, you can do it in writing. But would he really, if you sold it to him well? Used photos and would let him take them for example. That could be interesting by the way. You would see how he sees school, or dinnertime or brushing teeth. His perspective is likely not only literally different. 
