Erin I hope you or his estate can afford to get the flat cleaned out and you don't have to do it. There's often something left even after we detach from an ex, and your hurt is natural.
That he died in such a way is so sad. Some people just can't shake the addiction, or they think they're bullet proof.
Do you have some family or friends who can support you? If the estate allows, you might even be able to hire someone to help.