I don't know why you say "forget" all that you know about home brewing and use bread yeast. Yeast is yeast, and all of them produce alcohol and carbon dioxide..., it's just a question of how much alcohol you want to produce before the yeast stops, and if you want any other flavors. (I have baked with the trub from the bottom of the beer fermenter - trub is the crud at the bottom.) :shock:
Another observation..., your procedure ads yeast when the new mead is at room temp, but bread yeast calls for higher than room temps..., like 100º temps. You also add uncooked raisins. You do know that uncooked raisins carry wine yeast buds with them? That grayish, sorta frosty stuff you see on red or Concord grapes in the market, and you see the same on raisins in the box, a dull grayish layer..., that is from the formation of yeast buds. That type of yeast likes room temperatures, generally at the 70º - 80º range, if the yeast is a "wine" yeast. This is why one can crush grapes with the skin on, place the juice in barrel, and have wine several weeks later. True there is wild yeast in the air as well, but the dominant strain in the wine is normally the same as found growing on the grapes at the time of crushing and pressing.
So what you are probably doing is a double yeast fermentation.
The question then is ..., is the bread yeast out competing the raisin yeast, or does the bread yeast halt, and there are leftover sugars, and the raisin yeast finishes.
I noted you mentioned putting the container in a cool dark place, so you in fact may be fermenting with the raisin yeast alone, because low enough temps will put bread yeast to sleep. If the temperatures are under 60º, then the yeast may in fact be an ale yeast on the raisins or from the air, as temps that low put wine and many bread yeast strains to "sleep".
LD