He can use anything he wants to prove his case. It will be his legal burden to show whether or not the marriage was in good faith. It is up to the government to determine what weight the evidence carries and to determine if he is credible or not.
Yes, he can use all of the evidence he has to prove the marriage was bone fides. Because he will have to file for a waiver of the joint filing requirement, he has the burden to prove the marriage was genuine.
This answer is for informational purposes only and should not be construed as legal advice.