Is that an actual pic of what you are using? Why not use something like this? a four pack is under $8. I would grease the gasket to avoid tearing it. (because you are having a problem with that.) Also it should "pop" in easier.
via Imgflip Meme Generator
Edit: And by grease, I mean silicone O-Ring lube. something like this.
http://www.servapure.com/Lube-111-O-...FRaXfgodSpsD-A