It is literally Boehner's job to figure out what effect various things have on the country. If he legitimately has no position on that question, he isn't doing his job. Which is true, but still.
No, it isn't. It is his job to vote on subjects based on both expert and voter block opinion. It is impossible for one man to know everything about every subject, which means it is impossible to be a politician and know 100% of the facts of things you decide. This is why I'm quite tired of seeing college students scream out "HURR DURR SENATOR SO AND SO IS ON THE SCIENCE TEAM AND HE DON"T KNO SCIENCE!" Replace science with X subject and you get a bunch of crying nitwits angry that politicians don't know anything except politics. There is good reason that Congress has an entire army of experts at their beck and call. Ask those experts, don't ask the politicians, they're not going to know very much.
It is a vague question, no doubt. But that's their jobs: to take all the various question and impacts and condense it into a Yes or no vote. "Are we safer" is just a short form of "Does the Department of Homeland Security do the tasks they are assigned better than the various departments acting as they did before." It's a question he should be able to answer, especially as someone who needs to vote on justifying how much (if any) money should be spent on it.
And since be should have access to all the various attacks and plots that the DHS has foiled over the years, he should be able to answer the question with some accuracy.
I don't read "are we safer" as the question you extrapolated it to and John Boehner probably didn't either.