I have no idea what Fresco cheese crumbles are either.
Cream cheese here is sold in little "bricks", each one is 1 cup by volume (roughly) or 250g by weight. The reason they specify cold is that in many recipes where you use cream cheese, for example in a cheesecake, you're supposed to use softened, i.e. room temperature cream cheese, so keeping it cold might not occur to people.
3/4 of a cup of Splenda seems like a lot to me too. That's not far off the amount of sugar in most cheesecake recipes but in most cheesecake recipes you have 2-3x the amount of cream cheese, so it still comes out tasting a bit sharp. On the other hand danishes are often quite sweet, glazed and drizzled with icing, so that may be the flavor the original author was going for. I do note the recipe says to adjust the Splenda to taste, so in the end the 3/4 cup is just a suggestion.
Baking powder and baking soda are two different things! Both work as leavening agents though but not in exactly the same way. In my experience baking soda is actually lots more common to use than baking powder, but that may be a bias in the type of recipes I like to make. Different recipes need one or the other.