Fiction writers routinely take far bigger liberties than this with real life.
One I find amusing for some reason: The movie "The Wind and the Lion" is based on a real-life incident in the early 1900s in which an American, Jon Pedicaris, was taken hostage by what today we would call a terrorist group. In the movie, Mr. Pedicaris was played by Candace Bergen. That is, they turned a man into a woman. Before Caitlyn Jenner, even.
The movie "Argo", about a CIA operation to get six Americans out of Iran during the hostage crisis, shows Iranian authorities figuring out the plan at the last minute and chasing down the runway after the airplane as it takes off, creating a dramatic scene where the audience is supposed to be on the edge of their seats wondering if these people will be caught so close to escaping. In real life they boarded the plane and departed without incident.
Or to take an extreme case, the comedy "Which Way to the Front?" has a group of American mercenaries capture Hitler during World War 2, which you probably know didn't really happen.
And almost every work of historical fiction puts people at the scene who weren't really there. There are probably more fictional characters who have been placed on the Titanic than real passengers. Maybe that's why they didn't have enough lifeboats: they didn't plan for all the fictional characters on board.
The question is not whether you can get away with changing the facts of history, but how much? I don't think there's any hard and fast rule. Of course for an alternate history story you can change anything. Readers will give you more leeway for a comedy than for a serious story.
I think the guidelines are:
(a) The less well-known a detail is, the more free you are to change it. In your example, only the most ardent students of history would know off the top of their heads how many people were killed in that particular bombing. If you said it was hundreds, few would even know that was wrong. If you said that Pearl Harbor was attacked on November 7, I think lots of readers would be laughing at the error.
(b) You can change facts when they're relevant to your story. If you said Rommel was killed in Africa, and this "fact" has no relevance to your story, many readers would question it. But if there was some reason why you need to get Rommel out of the way for your story to work, I think most readers would accept it. You just need to establish the reason before the event, so the reader is prepared for it. More realistically, you can insert your fictional characters into events where the reader knows that no such people were there pretty freely. Readers tend to accept that fictional characters are, well, fictional.
(c) The more "serious" the story, the less flexibility you have. A screwball comedy can play fast and loose with the facts and the reader will just laugh. A story that is very serious and gets 99% of the facts right will be considered glaring if it gets one or two wrong.
I guess it also depends on your audience. A book about WW2 written today can probably get away with a whole lot more than a book written in 1946, because there are far fewer people around who lived through it.