Lori,
It sounds like you began with three possibilities.
1. Find the perfect PT who also has sensory integration certification and will develop the comprehensive plan for your child.
2. Find a PT who doesn't have sensory integration certification but still could help.
3. Be convinced no one wants to help, be paralyzed and hopeless.

Take a couple of days and if you can't find you can't find the first thing on your list I'd suggest moving on to #2 knowing that it could still be a huge help to your child.

I offer this advice as the parent of a teenager who has nearly identical diagnoses (plus a few more). It is great that some PTs are well educated in sensory integration, but we didn't have that option and therapy was still a HUGE HELP for our son. OT was also some help. Having a home exercise plan and integrating different types of movement and strengthening training into his life also made a big difference. Yes, he still has stuff he struggles with and it will affect him every day of his life, but he will still have a very good life.

I know "somebody has got it worse" isn't always a helpful thing to hear, but I will share that for our family spending a lot of time at the PT clinic was a good reminder of three things: 1. There are always reasons to be optimistic about improvement. 2. People are resilient. Your son is right, he will find ways to learn to adapt and that's a positive thing and 3. even people with far more serious disabilities can have good, productive and meaningful lives.

I would also think about whether or not some kind of help from a psychologist may be helpful. It is a fairly normal part of the process that kids with disabilities and their parents, can use some outside help and support to deal with anxiety and depression problems that can result. It sounds like your son has been having some struggle with figuring out what his disabilities mean and how he will cope with them and that's something a psychologist may be able to help with. Getting this type of help for family has been as helpful as OT and PT.