I am new to this forum, so forgive me if what I'm asking has been asked many times. (I did browse a little bit, and there is some good advice here.)

I'll start by pointing out that my wife and I are just about at the end of what we can handle. My son (6 years old) has SPD (we think), and he has been incredibly disruptive to the family. He is not malicious, but he gets very physical, he's loud, he interrupts, he doesn't listen, etc., etc., etc.

One very frustrating thing is that we don't get consistent feedback from the doctors. An OT was the first to tell us that our son might have SPD, but aside from her we have gotten a barrage of diagnoses, including motor dyspraxia, amblyopia, ADHD, and suspicions of mild cerebral palsy. One pediatrician told us that it all just adds up to the fact that we have a "quirky child." We have been to pediatricians, neurologists, developmental pediatricians, occupational therapists, specialized vision therapists, etc. No one can give us a straight answer about what is going on with our kid.

I am most resistant to the diagnosis of ADHD because he *does* have an attention span, especially while reading. (He was reading at a second-grade level before entering Kindergarten.) And now they are urging us to medicate him based on this diagnosis.

My son does have regular occupational therapy at school, and the interventions they have incorporated into his daily routine have settled him down there. They report that he is basically an angel at school--a perfect student (with occasional lapses, as with any 6-year-old). But it is a very different picture when he is at home. None of the things they tell us they are doing at school work very well at home.

So, I'm not sure what, exactly, I am asking here. There are a few issues that we are trying to work through: (1) how to get a clear diagnosis; (2) how best to treat him in the absence of a clear diagnosis; and (3) how to address his disruptive behavior at home (since we have tried just about everything we know).

Any suggestions would be like gold to us. We are at a loss.

Your son and my daughter sound like they could be twins, and your situation is a mirror image of mine. So sorry!! I know how hard it is My first step was to call one of the special ed teachers at school that I trusted and ask her if she could recommend a good OT. She recommended two. I called and told them I suspected my daughter had SPD and would like an evaluation. It was a two-hour appointment and within 10 minutes, she told me she clearly had SPD, and that was before she read the several page questionnaire they have you complete. Very frustrating because she had been in special ed preschool since age three, I kept asking the "professionals" what was wrong, and no one ever had an answer (Grrrr. Don't get me started! )
She had OT weekly for a year. Some improvements here and there. Then one night searching the web for the very reason you state in your post ("at the end of what we can handle"), I found a program called the Feingold Diet. It was very, very difficult to start, but not as difficult as dealing with my daughter. Within two weeks on the diet 100% she stopped having meltdowns, she payed attention more (better, but not super), and I felt like I could at least breath and relax a little more (no longer at "the end").
I also tried a home exercise program I found online called Ten Gems for the Brain. We saw some improvement in focus when doing school work. We also added probiotics to her diet, and they bumped up the focus a little too.
She was still plagued with low attention span, very impulsive, no safety awareness and limited social skills. Again I asked the school "what is it?" Then came the ADD diagnosis. I enrolled her in an alternative therapy program (very expensive, but we took it out of some money she inherited from her grandmother for college because I don't see college in her future the way things are going now). You can look at the program if you're interested at BrainBalanceCenters.com. She has only been in it three weeks, and it's a 12 week program, so I don't know if it will help.
I wish you well. Keep searching. There are a lot of programs out there, but it takes a lot of searching to find them.