1) I honestly have no idea...."buttery" isn't generally a term I associate with beer.
2) I haven't done a fruit beer yet, so I'm not sure. Seems to me like adding fruit to the secondary will activate your yeast again, yielding a dry character with little actual fruit flavor. If you do this, I'll bet using that 1968 yeast would be the best if you want to retain some sweetness. It's really flocculant (drops out quick), and isn't a great attenuator, so it'll likely leave some sweetness and fruit flavor behind.
Hell, maybe using that yeast will get you the results you want all around?
Dunno if that's worth much to you besides a bump to the top.
Welcome to the forum!