How to do a secondary only yeast

I am trying my hand at a sour.  I'm using SA-05 with my malts and hops in the primary.  I will use gelatin to help filter, and rack to a secondary where fruit puree and Brett will be added. 

I've seen numerous posts on the lack of fruit puree.  Is the best way to go to still add a cutom LME?

Can Beer Smith calc the abv for me? Of course I can take readings but I had wanted to tweak the recipe using beer smith before making it.

Thanks in advance

Depends on the specific Fruit.  try this chart.

http://www.hbd.org/brewery/library/SugAcid.html

Calculate the pounds of sugar based on the percentage from the chart.  Then I would add it as a Grain Ingredient as type SUGAR.

Also, you'll be adding water when you add the fruit.  Most fruit is 80-90% water. 

http://www.ca.uky.edu/enri/pubs/enri129.pdf

As a natural product your fruit will differ from the above tables.  So, expect some variation. 

PS:  If you check the "add after boil" checkbox when adding the puree ingredient to your recipe, then beersmith will place the fruit puree in the fermentation section of the brewing instructions (instead of the boil section)...but, it still has the desired impact on final ABV.

PPS: When you add Brett to your recipe, there is a checkmark "add to secondary".  Check that.