From the East Coast. My son is now 18, in 12th grade. DX: ID60/Autism/ADHD/LD/Sp&L/OT/PT. As a parent I can relate to every word you typed, except homeschooling. I highly recommend you find an advocate to help you for the next 10 years. Your son needs a curriculum that meets his needs, one that can move slower (cognitive delays means your son can learn but they process slower, slower thinking time, ie "I don't Know" usually just means he is thinking about the question asked and starting to formulate an answer and then needs to think about how to respond. Does he not know the answer or need more time to THINK??) I found Repetition is essential. So a curriculum that has repetition build in and adds a little bit of new each day. Right now...You are looking for the foundation skills needed at the elementary level. Once Middle School starts, school pace picks up quickly and he can get left behind, frustrated and behaviors will also be seen. I recommend to Repeat school work at home on the same day to help repeat and master skills. For example, we created 2 reading classes a day and 1.5 math classes a day then I got copies of all materials sent home. My son had a 1:1 support person to help. You might ask yourself if there are 30 students in a class and one teacher how can repetition happen at school.
As for the IEP meeting, the IEP is not final and you can have more than one per year. The right time to ask is right now. You are the main person directing the IEP team. Do you have Test scores in all areas to see his baseline grade level, strengths and weaknesses and to help guide the IEP team? An advocate can help you requests the right tests and support you during the IEP meeting. Ongoing frequent testing is necessary to see if the curriculum is working for your son and he is making meaningful progress. Collecting data and numbers and record keeping are a must. I asked for homework of the work he does in school so you can see how your son works and help you to guide the IEP team and staff to what works best. You know your child best. I always go to the IEP meeting with a list of what is working great and what is not. I write all this in my parents concerns and give to the school before the meeting so everyone knows what My goals and priorities are ahead of the meeting. FYI-My meetings were always 2-3hrs. If someone needed to leave and you need them to stay then reschedule another meeting time. I also include my recommendations what I think will work best. I ask the team about what curriculums can support my son and then look them all up when I get home or ask to see samples of them. As for modifications and accommodations there are thousands and the answer is it depends. Look up the meanings of these words, you may need both. Your teacher can provide you with a list they are probably already doing. Ask for a list. I would make copies of the blank worksheets and find out if he can do the work and then try to figure why they are blank. Did he run out of time, was he distracted, did he understand, etc.
You really should take the ADayInOurShoes IEP advocate class. I wish I had it 10 years ago. Your sons Diagnoses are lifelong so educate yourself for small amount of money and then you will know how you can help in a positive way. As parents we get emotional so that is why an advocate is a great idea. FYI- My son finished modified Pre-Algebra curriculum in 11th grade and reads with support at 9th grade level. Inferencing is still difficult as well as writing (He still has 2 ELA and 1 writing class each day). He attends a small HS and has 2-6 students per class which is the perfect size to decrease distractions and get repetition and support.