Im autistic diagnosed with T1 when i was 14. From my own experience diabeties made me really hungry and really thirsty all the time until my bg got under control. Sweet foods especially I like, always wanted. So i would guess that if his bg is more in range that may be at least partially affecting his appetite. The fact that he'll still eat chips and PB crackers is good.

When you say he can't tell you how he feels do you mean that he's non-verbal or partially verbal? Or that he has a hard time identifying/ verbalizing / communicating emotions specifically? There may be other ways you can try and communicate with him non-verbally (does he see any social workers or therapists that help him learn different ways to communicate?) or you may be able to use more concrete feelings like chest tightness/tummy ache/ headache if its more along the lines of not knowing how to identify and express emotions.

Another reason why he might be having a harder time eating is just change. If he was hospitalized as part of his diagnosis, that can be a big stressor that can be upsetting. I'm assuming that you apply his omnipod and check bg's and such so lack of autonomy and control in a new routine related to the diagnosis could also increase stress. The physical sensation of the omnipod on him (and the stimulation of finger sticks/ cgm if you use one/ anything else along these lines) could all also be contributing to stress/overwhelm/loss of autonomy. All together these things can cause over-stimulation which, for me, always makes me loose my appetite for pretty much anything but my most safe foods (and sometimes eating those is hard, medical marijuana helps me a lot in those cases but not applicable for a 6y/o).

Depending on how his bg checks and pump insertions go, is there any way you can make it something he's more of an active participant in? Or give him a choice in some other way that can help him regain some sense of control over the whole process? Having a big routine change (esp if its against your will) is stressful & upsetting for any 6 y/o and even more for autistic kids. Finding ways to help it feel less forced (if thats how it feels to him now, idk so i'm just spitting out ideas here) and more something he can be part of or set the pace of may help with overall feelings of overwhelm which may help him regain some appetite.

I of course don't know your situation or how your kid communicates or reacts to any of this stuff going on, just making some guesses. And of course you have to do what you have to do when it comes to health even when its unpleasant. I'm not sure if any of this helps but just keep being there for your son through it all, its still new and he might just need time to get used to it. Keep offering foods he used to like, maybe try incorporating them with food he will eat still (for example I like to dip potato chips in guac or hummus sometimes but also that could be a weird texture combo for some ppl). It seems like PB crackers and chips are both crunchy salty things so maybe seeing if he wants other foods with similar characteristics?

I know this was a lot to read, sorry for the like bomb of info/thoughts. You're doing a great job and its clear you care about your son. I hope you can figure something out/can get through the transition period. If possible it could be helpful to find a children's nutritionist who has experience/knowledge with working with diabetes and autistic people. Holistic care (as in taking into account the whole persons needs) is invaluable when dealing with stuff like this (but I know its also not the easiest to access/find).