Before I get into any details, I would like to be crystal clear again that I condemn terrorist attacks of any form against anybody, be it Christians, Atheists, or Muslims, for any reason - including this attack of course.
Now to your point, I would agree that at its core, there are similarities between the three religions. I would say the biggest difference between Christianity/Judaism and Islam is that the former has gone through reformation to marginalize the bad parts of their holy book to fit modern secular values, while latter hasn't done so. Which is why you hear of lots of honor killings, throwing gays off buildings, killing anyone who leaves/blasphemes Islam in the Islamic world, and not practiced by anybody who's a Christian or a Jew - if there are counterexamples, it should be extremely marginal in comparison as far as I'm aware. I doubt, for example, there was anyone who performed honor killing in the Western world by a Christian/Jew citing Leviticus (terrible book, by the way) or any other outdated book in the OT in the 21st century while there are dozens of instances in countries like Pakistan.
Also, let's take a look at the prophets of Christianity and Islam, respectively Jesus and Muhammad. As far as I can gather from their respective texts, Jesus has never encouraged violence (Muhammad did), never tortured anybody (Muhammad did), never killed anybody (Muhammad did), never had sex with children (Muhammad did), never launched military campaigns (Muhammad did)... list goes on, I'd gladly continue until I run out of examples I can think of. When you look at the actions of these two prophets, it's not too surprising to see some of its followers behave accordingly, even today.
So what can be done to solve the many flaws in Islam? Obviously the solution to this issue is more complicated than it first appears but one popular proposal is reformation - I think it's important to give people like Majid Nawaz (pretty sure he's still a Muslim, just deradicalized), who has different opinion on Islam, a voice instead of demonizing them as "anti-muslim infidel". Islam as we know it may be completely transformed should this "reformation" succeed, but it's infinite times better than this radical BS that doesn't, and will most likely never conform to modern society. One thing I know is that labeling those who criticize Islam as "islamophobes" is going to help no one. (I know you haven't done it but it's such a common ad hominem that I have to address this)
tl;dr - Islam is worse than Judaism and Christianity, even if there are some similarities.