Reformulate a marshmallow recipe to remove lactose and HFCS
I think you're taking an overly complicated approach to this, I've had great success with a recipe from the DIY Cookbook from ATK, in their version, they use:

confectioners’ sugar,  cornstarch, unflavored gelatin, corn syrup (not high fructose), granulated sugar, salt, vanilla extract

The only non-vegan ingredient in this manifestation is the gelatin, which you can sub using many different vegan gelling agents. 

Here is one website detailing the recipe procedure: http://www.thefrugalgirl.com/2012/11/how-to-make-homemade-marshmallows/

As well as a post on "The Feed", an ATK website with a video: http://www.americastestkitchenfeed.com/do-it-yourself/2013/01/how-to-make-marshmallows/