OP I am so sorry to read this.
couldnt read and run, though I may not have a great deal that is helpful to offer in this situation I wanted to reach out for a virtual hand hold.
My son is ND, and I come from a family with quite a lot of ND of a variety of shades, so I have a little insight if not the full experience you describe.
My first question for you is do you have any support in the form of (a) Portage and (b) outreach from the early-years outreach team associated to an ASD school in your area?
you should be eligible for both of these things - you can try referring yourself through the local children’s centre.
secondly, do you have access/can you get access to Occupational Therapy (OT)? This made a MASSIVE difference to us.
you ask is there any quality of life - the answer of course is YES, and while it may not seem like it right now it is there.
i can only share my experience, but we had many intersecting issues going on- with sleep deprivation being a massive one that was foundational - before he was well rested things seemed to be going backwards - after getting solid sleep (and us too) everything gradually got easier . We were supported by a sleep training programme (Batelle) that had an ASD Specialist on staff who supported us to customise the approach and provided 1on1 support for difficult behaviours that ramped up during the programme. we accessed this privately, but I should imagine with some inventive googling that you might be able to find a plan and perhaps through portage meet some other parents who can act as a support network for this step
then on top of this, OT in particular helped us understand some other priorities and create some strategies to support is to manage these and increase his “tolerance” for a wider range of activities.
DS’s sensory overload (sounds like this may be an issue for your DS from what you describe) was particularly around sound - headphones helped him a great deal.
you describe a very limited list of “safe foods”. If you haven’t done already look up support for children with ARFID.
it may be that you chip away at the various elements slowly but surely to turn down the “extremes” of your DS experience of the world, which in turn should help him turn down the “extremes” of his behaviour.
When I was a child my brother was supported in a very similar way by the local Barnados centre. I am not sure if they still provide these early childhood intervention services - worth looking into though.
all of this is so hard, OP. Parenting an ASD child can be really isolating, but you’re not alone.
it does get better.
DM if you need xxx