[InSovietRussiaORGASMGotU]

I don't see it as a problem if you go to a Christian church, although if it's an extremist church then I'd probably not mention I'm a non-believer. If it's not an extremist church, then why not? Some people there may not approve but overall, a church is simply a public meeting area.

You don't need to adhere to a certain religion because generally the word "religion" is associated with the belief in a god/goddess. Whether or not that deity is all-powerful or what that deity does isn't all that important so I'd rather term it having your own philosophy. In that case, I'd say humanism, shinto (more of a spiritual idea), LaVeyan Satanism, etc... .

Or, instead of finding a religion or philosophy that you like, why not invent your own? You can in a way blend some ideas from various philosophies combined with your own beliefs.