I assume you fix the math errors and then whatever the result is turns out to be the justification for the decision. The result doesn't matter, so you don't need to aim at a particular one.
Neither. You report what you found. You make recommendations. You state which areas you haven't had the time to look at. Under no circumstances do you provide any guarantees that might put you at the wrong end of a multi-million dollar lawsuit.
This, incidentally, is every audit ever. I've been audited many times, every audit finds stuff and make recommendations. Then management gets to pick which recommendations they adopt and which they'll derogate. I'm not saying it's a completely useless process, but it doesn't provide the cast-iron guarantees people think it does.
Then, of course, there's financial audits, which are meant to provide a cast-iron guarantee the firm is still a viable entity. But nearly every big firm that went bankrupt had passed such an audit in the previous year.