What do you mean?
No such thing as a sponsorship for a tourist visa. You could be a millionaire and he could still be denied.
That evidence has to be submitted at the time of applying.
The consular officer is in no obligation to ask for more proofs because, again, that evidence should have been submitted prior to the interview.
Why is he so desperate to come? Applying multiple times will actually prove that he is desperate to come. He needs to wait a few more years, and reapply when things have changed for him and he's more established elsewhere.