Theresa May is pinning the spy and nerve agent situation on Russia... false flag?

Most of the top posts in the worldnews subreddit right now have to do with a spy being killed by nerve-agent, and how Theresa May is going to pin it on Russia.

I guess I have a few questions about this situation...

First off, WHY would Russia bother with nerve agent? It seems extremely over-the-top, cold-war era, super super obvious, might as well have left an autographed picture of Putin on the scene as well. If I were Russia, and wanted this guy dead, wouldn't a bullet have been easier, and less suspicious? Or maybe just put the guy in a locked duffel bag in his bath tub, because nothing wrong was found the last time that happened.

Second, what evidence do they have that it was Russia? At least right now, the public only knows that it was a nerve agent. Where did that nerve agent come from though? Do we have communications that say that Russia was directing its use?

Third point, and really related to the first question, if I were Britain or the United States and I wanted to create a false flag operation to make people angry at Russia, isn't this kind of thing the perfect situation for it?

I'm not saying Russia didn't do it. Most likely, the intelligence community has some sort of actual evidence that points to Russia that isn't privy to the public.

But. This really sounds like something we should be certain about, instead of jumping to the obvious conclusions.