I have dealt with Sciatic pain for four years. I also have compressed cervical vertebra that has caused nerve root inflammation, right now it is so bad I need a walker to support myself, yet I am improved enough to return to work after a three month medical leave.
Do not under estimate Owen's suggestion about water. Your son needs to be drinking a lot of water, preferably distilled.
The second thing is anti-inflammatory supplements and foods. Your son needs to stop eating all sugar, white flour,indeed most grains, most dairy and most if not all meat. All of these foods feed inflammatory conditions and also tend to make the body acidic which also promotes inflammation. He need to eat a lot of leafy green vegetables, yellow, orange and red fruits and veggies and purple grape juice. If he is not willing to eat these things, then please consider getting him on a green drink or "Superfood". Owen introduced me to a product called Green Max from Swanson Vitamins, that has turned my life around. I mix a tablespoon of Green Max powder in 10 ounces of distilled water, and add 1 tablespoon of apple cider vinegar (raw is best), 6-10 drops of cayenne tincture, 1-2 teaspoons of sorghum, a pinch of Sea Salt , a pinch of Epsom Salts , and a pinch of cinnamon, and two grams of sodium ascorbate powder (vitamin C). I shake it all together and drink it down. This last week I also began adding 2 tablespoons of fresh ground golden flax seed to the drink once or twice a day. Flax seed is high in Omega 3 Essential Fatty Acids which are very powerful anti-inflammatories. The Green Max has sea weeds for minerals and powerful anti oxidants. This is a very healing drink and since your son cannot take pills or capsules it might be a real help for him. Spices like turmeric, ginger and cinnamon are also anti-inflammatory. The key to natural healing of a problem like this is an alkalizing diet high in minerals and antioxidants, flax oil, or if he will take it fish oil or tuna, salmon or sardines for Omega 3 EFAs, plenty of fresh pure water along with the elimination of coffee, tea, soft drinks and most sweet fruit juices, and also stretch with only the gentlest stretches, high impact exercise and strenuous stretches need to be avoided when the nerves are highly inflamed. Once the inflammation is resolved exercise can be increased. My Chiropractor uses Ultrasound and Diathermy on my spine, he does not do heavy traction or adjustments, he says that does more harm than good when the spine and nerves are swollen and inflamed.
I hope some of this will help. I am not healed, but I am going in the right direction. A couple of months ago the pain was so bad I was literally screaming with every movement and usually had to crawl like a baby because walking was so painful and difficult. Like your son I wanted to do everything I could to avoid surgery, my intuition says it is the wrong thing to do. I have also fought to stay off steroids. You son is still in for a long hard road, but hydration and good diet will do more to help him than anything else I know.