I don't think there is any right answer. But I can understand your DH response to you saying half to your dd, and nothing for his. For him all three are his dd, and its an understandable emotional reaction. For you its equally understandable, given what the dsd can get on the other side from their mother.
I don't know what policies you have in proportion to the house. Each of mine are about equal in value to the house. (I figure house all paid, policy for cash, policy for tax liabilities, pension in trust)
Can you not compromise and do a 1/3 each on the house but keep the policies for dd1?
If not, then I can only suggest you sit down and discuss it from a point of view that if today you both went, then who needs what.
e.g. DD needs the most as other relatives/people would be looking after her and she is 1, DSD2 the next by age but has mother, and then DSD3 by virtue that she is grown.
Don't include that they would inherit from others though, stick with what each need from you only. (Saying that to avoid some of the emotion)