I get your symptoms when consuming lactose, but also get gas, etc. from gassy vegetables. I'm OK with salad, spinach, rice, but have to watch amounts of corn and avoid beans, including soy products, and cruciferous veggies like the plague.
My situation is complicated because I am also intolerant to sulfites, allergic to sunflower seeds and maybe some nuts. I get the usual allergy symptoms from sunflower seeds - swelling in the throat, plus my usual intolerance symptoms of gastric reflux followed by tachycardia. Usually I can get the tach stopped with valsalva maneuvers or coughing, but last summer one lasted 5 hours, required a trip to the ER for adenosine heart conversion.
I feel a lot better if I avoid wheat. I am happy though, to be able to eat oatmeal and rice, including rice crackers. You have to read ingredients on rice crackers because most aren't all rice!
After you've been off dairy for a while you might try lactose-free again. I thought I couldn't have dairy, but have no trouble with the other proteins. I also tolerate some of the softer cheeses in small amounts and Activia yogurt. Good thing because I really can't have soy! Soy products generaly have sulfite. They also give me gas.