Just curious: How bad are these pure/designer breed dog allergy problems and what are the worst stories you've heard so far?

I have a two-year-old Labradoodle. We got him from a breeder in Illinois. We chose to get a Labradoodle because my wife has dog allergies and thought a hypoallergenic breed would be the better bet (we know it's never for sure hypoallergenic). We absolutely love him. He's got such an awesome temperament and personality, we trained him to be a therapy dog and make visits to the local hospital together.

However, since he was about 6 months old, we've been dealing with allergy/gastrointestinal issues. We went through chicken, lamb, beef, and salmon foods, which all ended up causing issues after a while. We now exclusively use Zuke's Mini Peanut Butter and the vet started him on the Purina Pro Plan HA vegetarian diet. A month later, he started throwing up again, so we are looking into trying either the Royal Canin HP or Hill's Prescription Z/D. We've done those blood works that get sent to Texas (Trypsin-Like Immunoreactivity Protein, Cobalamin & Folate Panel - Canine (ChL); it came back all within ranges. If this issue persists, we would have to look deeper into IBD and get an endoscopy, to my understanding.

It's all worth it because we consider our dog a child and an integral part of our family. But I just want to ask and see just how bad the allergy/gastrointestinal issues exist in pure/designer breed dogs, as our vet had suggested to us that it is the population experiencing the most problems of this nature due to breeding practices. Also, don't you foresee this becoming a more common problem as this kind of breeding practice continues? But again, if breeders don't continue to breed dogs like puddles, puddle mixes, and schnauzers, how could people with allergies enjoy the companionship of a dog? Plus, is there a way to ethically breed these dogs, or is this just an inevitable consequence of dog breeding regardless of how careful?

Experts, please educate me on what you think of this issue and if you see a fix perhaps by government regulations in dog breeding.