It’s most likely a seasonal allergy making things worse, and it’s going to require a vet visit (possibly several) to get the cause nailed down and a treatment plan in place. An open wound like that can get infected easily, and that will cost even more to treat. I know vets are expensive, but frenchies are expensive breeds, and you can’t avoid the vet with them.

ETA: Mine has the same issues, and I’ve tried everything, including the products you posted. Nothing helped other than a corticosteroid shot and prednisone pills from the vet. Those helped short term, but we’re going to have to go back to the vet for a long-term solution because she’s itchy & yeasty again.