It's okay, LennaB. There's a whole world of opportunities out there, and lots of good friends to be made that may not even be Christians, let alone JWs. You haven't done anything that can't be undone. It's great that you've realized your mistake this early. I've been in the religion continuously for three decades and haven't been able to leave yet, so just take this as a major life lesson and be thankful you have so many years ahead of you. You'll never fall for this stuff again!
Anyway, I'm impressed with your earnest pleas to the elders to answer the troubling things you'd found. Of course this is the reason why Witnesses aren't supposed to go onto sites like this, and are discouraged from reading old literature. There's a lot of stuff back there that even elders today don't know about; all they know is that when people look at that stuff, they "fall out of the truth". Rather odd that God's organization would be allowed to publish things which, all on their own, would later stumble his people, isn't it?
Don't let the scripture about the Devil transforming into an angel of light cause you any concern. It's not inherently very meaningful because, well, if we can't tell the difference between the Devil and an angel of light, what hope is there for any of us? Likewise with the scriptures about not leaning upon our own understanding, and the treacherous heart. These scriptures are of course not wrong per se, as it's a bad idea to only rely on your own understanding. But as used by the Society, they become thought-stoppers; "don't worry that little head of yours, we'll tell you what's right and wrong".
After all, how can we be told not to trust our own heart, when it's your heart that led you to the religion in the first place? At what point did it stop being trustworthy? Only after you started studying? What sense does that make?
Anyway, I know you must be an emotional mess right now. Just be assured that you can move on from this, stronger and better than ever. Please go ahead and make new topics for any questions you have (of course a lot has already been discussed here, if you search around). You will be amazed at how much there still is to learn about the Bible, science, other religions, you name it. I know it's been a real eye-opener for me personally.