You are right. We don’t have anything concrete that says he is legally able to hold the office of POTUS. He wasn’t vetted.
Before you say/type another word on the subject, read this post and study the linked images.
At this point, sufficient legal vetting has occurred. Insofar as circumstances, doubt & irregularities abound, none have provided compelling legal proof of ineligibility. (Don't get me wrong. There's a difference between supporting the !@#$% and acknowledging that one's opposition may actually have the upper hand in the dispute.)
We now return to our previously scheduled thread...
If you DON'T answer all the questions, and are duly fined, that may very well give you "standing" to challenge BHO's eligibility (per the above blather) to compel you to answer those extra-Constitutional 4th-Amendment-violating questions.