I come from a family who own a trading business, and in our family we have a saying about doing business with friends and/or family members (at least those family members who aren't part or closely related to those taking part in the business) (FnF):
FnF make bad business relations. Expectations are often not realistic
and thus disappointment is usually a big risk, and if bad things
happen one which will continue to haunt you even after business is
Also, they usually try to play on your emotions to get (too
much of) a bargain, usually way past what can be considered rationally acceptable
If you still can, you should set out a framework for doing business which puts the assignment outside your personal relation with your dad. This will enable you to approach your work with a better understanding of what each party (i.e. you and your dad/his company) can expect of each other, and makes it easier to place and evaluate demands each party has.
In any case, you should make clear that you cannot proceed without more contextual information and tell him his behaviour is somewhat unreasonable.
You have to explain to him that his non-cooperation is acting as a blocking factor to your work.
I'd also phase your work planning, with several go/no-go decision moments if you still can.
You might try using ARM, tracers of some other pitching methods mentioned to get a foot in the door.
When he rejects the possibilities you pitch, reiterate that without proper information you cannot create a good/better product, and make clear that your product has a much higher chance of not meeting expectations because of that.
The knowledge (knowhow/knowwhy) you have cannot be applied without knowing what to do (where/what within context). To make it tangible, you could use an analogy of a truck driver who needs a map to get where he needs to go.
If he fails to comply, I'd dump the assignment if possible.
It's probably very hard to fulfill the expectations if you don't know what to aim for.