You're not the first and you certainly won't be the last person concerning themselves with how to break the Bitcoin network.
You should use your knowledge and skills for productive means and help the community.
What exactly do you think computer security professionals DO? Or cryptologists employed by three-letter agencies? Or military strategists?
A person who wants to strengthen the bitcoin network and
isn't constantly thinking of ways to break it, isn't doing their job.
I wish more people understood this concept. This type of testing is exactly what bitcoin needs to become stronger. You have to think of different ways to attack bitcoin in order to develop better ways to defend it.