Hmmm... probiotics have always reduced gas for me. I can't even remember the last time I had it since doing our intensive gut overhaul :LOL
Maybe it's the bifidus and you need more acidophilus. I believe it's the acidophilus strains that help digest the lactose in dairy by making lactase in the gut. Are you okay with dairy at other times? I do know bifidus is for the lower colon, where the problem seems to be for you.
However, I do know when yeast cells are dying, they do give off gas. It could be the die off, called the Herxheimer Reaction. The more yogurt you eat, the more the die off symptoms, but eventually the good bacteria should take over.
I would give it more time. What powder are you using to culture? Perhaps you want to try a different one.