If your husband is insisting on a private school, religious or not, you may be facing an uphill battle getting the necessary services. If you are in the USA your local school district is obligated under federal law to provide a free and appropriate public education (FAPE) under the Individuals with Disabilities Education Act (IDEA). Private and parochial schools are not. Child find obligates the local school district to identify children who need disability services but they may or may not provide those services if your child is not enrolled in the public school. Some districts make the process easier and/or are better at providing the needed services than others. Your first step should probably be to contact the director of special Ed in your local district and see what they say about starting the IEP process regardless of whether you enroll him in public or not.
My DD10 attended kindergarten at a regional magnet in the neighboring large city. It was an awful, awful experience. I had suspected fine motor and hand/eye issues from the age of 18 months, dyslexia from the age of 4. All anyone saw was the sparkling brilliance, though, so it was very difficult to get referrals for evaluations or services. The district where the magnet was located would not do anything - they just kept repeating "she'll never qualify for services she's too smart." Finally at the end of the year I contacted my home district and they did testing to find results similar to your DS.
We wanted to enroll her in a lovely little private school that we were sure would contain the anxiety. My school district talked us out of it saying she *had* to be in a a public school in order to get all her needs met. They explained FAPE, IDEA, LRE, child find, etc. If the private were located within the area my district serves they would be able to oversee her program and offer limited services. (ie up to 45 minutes per week reading intervention as opposed to the 2.5 hours she would receive at the public.) The private was located in the same city where DD had done kindergarten so it was clear they would not provide any services to a non-resident attending a private school within their borders, We would be financially responsible for all services and devices she may need if we did not place her in the public. Once our total got to be $50k for first grade (and still counting) we realized private was not going to be a viable option. She is now in an out of district placement at a special Ed school and I estimate her yearly expenses to be in the $80k - $100k range. There is no way a typical family could undertake this. Even with good insurance and good income it would be unreasonable to expect to do this year in and year out.
So in term of where you start - assuming you are in the USA - call your school district Monday morning and ask to speak with the director of special Ed. It's a tough time of year because all the back to school IEP and 504 meetings will be happening the first weeks of the new school year. Meet with them, show them the neuropsych eval and ask for direction. You will likely be needing OT, speech and reading interventions to start. You will also need to start looking for a private therapist. The public would probably provide counseling with a school psych or social worker but with the kind of trauma your DS has likely endured you need to find someone who is experienced with 2E/ school anxiety issues. (We got lucky and found someone who specialized in school phobia and was a 2E adult and the parent of a 2E kid. She even took our insurance. Not everyone is that lucky.)
Then get very, very familiar with Wrightslaw. There is a steep learning curve on all of this and you will feel overwhelmed. Everyone does. Just keep reading and learn as much as you can. Maybe bring in an outside advocate to help you figure it all out. On Amazon you can buy 3 of the Wrights' books bundled together that will explain special Ed law, IEP's and how to advocate. They would probably be money well spent.
But really - if your husband insists on keeping your son at the religious private this is probably going to be very difficult. Meet with them too and show them the report. They may have at least some of the services available even if you have to pay extra for them. They may tell you that they can't meet his needs for the reasons outlined above. If they dismiss the report or continue with the negative labels that would tell me that he *can't* be successful there.
And keep coming here and asking questions. Chances are pretty good that someone here has been through whatever challenge you will be facing. Even if you just need to vent we are here. It's hard to find people in real life who will understand so luckily we have each other on this forum.
Good luck!