i also work with bottles. i would fill them more to the top. this would leave less space for oxigen, but the drawback is the foam and if you are going to give more sugar into it, it will be a mess.
and yes, bread yeast is not that nice. tried it couple of times but the taste was not nice. wine yeast is inexpensive and i like its taste, i also like to drink the federweisser because of the taste and of the the minerals and vitamines containing in the yeasts.