Hi and welcome!! I am sorry you needed to find us, but happy to meet you just the same!!
It sounds like you have several problems going on. I completely agree that allergy testing can be worthless. I react viciously to a LOT of things outside, esp lilac. A few years ago I had allergy testing done and I reacted to NOTHING but the control stuff. Allergy medications still help me, but the doctor says that MANY people are sensitive to things that don't show on tests. It sounds like you are going to have to keep a lot of the things your child reacts to out of the house. You can try to substitute other things, or make your own versions of what he likes without the things that bother him. I make a LOT of things from scratch, or from homemade mixes and it has made a HUGE difference in my family's life. I can recommend some books if you want to try to make mixes with-o food color, preservatives, corn syrup, whatever. The elimination diet is really the ONLY way to tell if a food is causing a problem.
School is starting soon. You will likely need a doctor's note to keep your son from having certain foods. For years my youngest could not have dairy, tomatoes, oranges, pineapple, strawberry or artificial sweeteners of any kind. Now he does well with dairy and tomato, but avoids the others (they don't taste good to him, thankfully). I kept dairy free cream cheese and crackers at school, as well as a few packages of snacks/treats and juice boxes that he could have. It has never been a problem as most teachers have small fridges in their rooms. I got one donated for the only teacher that did not have one (first year teaching). My son did not react to corn so I got a microwave popcorn popper and a big bag of popcorn with some seasonings for the class to share whenever they earned it. Cost about $25 total and then thank you did not feel like he was different or deprived.
Finding substitutes that the kids like is a HUGE help with food problems. If dairy is a problem (it often is, and can be hard to pinpoint because dairy is in SO many things), Tofutti makes some AWESOME products. We like the tofutti cream cheese better than regular except for cooking. Tofutti ice cream sandwiches are INCREDIBLY - I had to fight to keep everyone else in the house from eating them (including ME)! Stores like Whole Foods even have candies that he may be able to eat.
If he likes lemonade it is easy to make from scratch. 1 cup lemon juice and 1 cup sugar with water to make 1/2 gallon. You can use artificial sweeteners and use less or more of the juice and sugar if you like. My kids like this better than fruit punch or whatever. So do their classmates, and it is MUCH cheaper than buying punch for a class.
The problem with your husband is not so easily solved. The counselor is right that this will end up creating a HUGE problem as the kids grow up. Parents MUST present a united front if the kids are to grow up with-o a LOT of problems.
Many, if not most of us have been there. It took YEARS to get it through to my husband that he HAD to support me the way I supported him. I once described it like a dam. The child is the water rushing at the dam doing all it can to get out and cause havoc and destruction. The destruction would be the bad behavior and the ruin of our entire family. I was the one who set the rules and enforced them and did the various appointments, etc... I NEEDED him to support me. I was a wall standing there containing the constant pushing of the water. He was the support that helped me stay in place. Unless I could depend on him to shore me up and provide a second line of defense to keep the difficult child stuff in check, the dam would fall and the entire family would end up in ruins.
It was graphic enough to let him SEE how his giving in was hurting not just my feelings but our entire family, including his relationship with me.
I also had him read "Parenting with Love and Logic" by Fay and Cline. It made more sense to him, and to a lot of my friends' hubbies, than most other parenting books. It is pretty no-nonsense and stresses the use of natural and logical consequences while preserving the loving bond between parent and child. For us it was the book that let us get on the same page speaking the same language. Men and women approach parenting very differently, in my opinion, so this was crucial for us.
Do you think there is more going on with your child than just the inconsistent parenting? We don't put much value in an ODD diagnosis because it doesn't really tell you anything. ODD means the child is badly behaved. It gives NO insight into why the child is doing what he is doing. Almost every single difficult child here has had an ODD diagnosis, regardless of whether their problems were caused by bipolar disorder, an autism spectrum disorder (Autism Spectrum Disorders (ASD)), a medical problem, an allergy, or past trauma or something else. I recommend having your child tested by a neuropsychologist if you think there are any problems besides the parenting issue.
How was your son's development? Does he have friends? Does he line up his toys rather than playing with them in an imaginary way? Why does he have the rages/tantrums (best guess)? These are a few of the questions that can help you figure out if testing is needed.
I hope some of this helps. You can learn more about Love and Logic at
www.loveandlogic.com - they have many books and even some free items on the site. The books can be ordered through the website or found at the library, bookstores, etc...