Oh god... I think we're having a non-volatile discussion. I'm gonna take a deep breath.
Okay...
touching on not ruling out the spiritual realm... I see what you're saying. It's why I think anyone who says they are 100% atheist is lying to themselves... just as any religious folks who completely rule out the possibility of being wrong are simply afraid of the dark truth that this life is all one has. Ignorance goes both ways. The main point here is that none of us know the answer because it has yet to be uncovered, therefore we should always keep our minds open, which is why I've studied religion as much as I have (both in school and on my own accord... I'm a curious soul).
I was only semi-sure about question 15 because I learned that at some point in high school... it was definitely a doozy.
As far as prayer... I myself have tried meditation. Specifically, I've used the method of chanting the name of god relentlessly until one briefly realizes god. I myself have done so multiple times for as long as 2 hours and never attained that realization. It is why I am convinced that I lack the necessary faith to be spiritual.
I have opened my mind to the concept of reincarnation more than any other religious facet strictly because I've experienced deja vu a great deal throughout my 21 years. If you ever take the time to look into the links between deja vu and reincarnation, you'll find it quite fascinating.
finally, in response to your inquiry about what one loses in devoting themselves to a deity... it goes back to what I said. If one follows a certain belief strictly because of the "might as well" factor, then what does that say about the strength of a person's faith? The vibe I get from it is fear. However, to answer your question... one would lose a great deal of time and energy in their (possible) one and only life if they were wrong. The way I see it, I've got another 50 or 60 years to experience the world; probably less. I'd like to use those years absorbing everything in the world around me without having to worry about the sins I commit or the sulfuric pits I'll burn in for taking drugs, committing adultry/premarital sex, lying for self-gain, or whatever trouble I've managed/will manage to get myself into.
Basically, I really hate the thought of answering to some celestial being and being punished for simply spending my life having fun.