I'd say you're doing this the wrong way. You're trying to do a mountain of inference on a mole hill of data. Take more data. This has been of my issues in life, and I've found life gets easier when I just ask. There is the concept of managing up - having to manage your manager, doing what you can to make sure your manager gets what they need from you, even if they don't know how to arrange that themselves. If they're incompetent, their incompetence is your problem.

First, you want to be adequately trained. Too many people focus on getting a list of what to do, instead of a list of the figures of merit. What are we trying to accomplish? What are our goals? What does a good job look like? What does a bad job look like? Stephen Covey distinguishes this as the difference between gopher delegation and stewardship delegation.

Second, instead of worrying about icebergs, ask for feedback, good and bad. People refrain from criticism often because they are uncomfortable giving it, and expect you to be uncomfortable getting it. They only bring it up when their annoyance with your failure overcomes their reticence about criticizing you. That's not going to be a fun talk. Preempt that, and make clear that you want to do a good job, and want feedback to improve. That way they can bring up issues before their annoyance has mounted. When they've done that once or twice and it's not a horrible experience, it gets easier for them to give you feedback in the future.