Heyla and very warm welcomes
as to your questions? well, at least for me, compersion didn't just happen overnight, it was difficult to "find", but what opened my eyes to it, was watching my closest friends and their spouses, whom are also poly, which has made mine and my hubby's intro to the poly world both helped and hindered. they are quite different from us and have a vastly different set of rules for their poly, but seeing them in person interracting with each other and their own loves, its truly a wonderful sight. that is what has made it a bit easier for me. I will try to get my hubby to come post in here as our steps into poly were harder on his side, he might be able to add some more helpful insight. some folks have compersion already, some of us have it sneak up on us when we aren't looking. it sounds like youve already had a taste, being sad cause your wifes interest did not return her interest. just keep talking and sharing, you will probably find it and feel it before you even realize it, its very natural to be happy when our loves are happy, give in to it and enjoy it.
as to the fears? we all have them if we're truly honest with ourselves, and I've found the best thing to do is simply sit and talk with your loves about any and all fears your having, its uncomfortable and can be intimidating, but often all these fears can be easily talked out if we just voice them and let our loves know whats bothering us. little small fears can turn into such monsters if let them sit in the dark and grumble for too long. speak up, get it out there, its often no where near as bad as we think it might be once its out in the open. keep talking, often this is said so much we must sound liek broken records, but you really can't talk to much, at least i haven't found theres such a thing as too much talking in poly. weather your starting out or have been poly for many years.
statistics to me are just that, a number on a piece of paper, that we really have no rule of thumb for considering we don't even know how many people made up the poll/census for said statistics in the first place. please don't let numbers on a piece of paper deter you from something you may want.
you sound very happy and determined in your current relationship, thats wonderful. you want to give poly a shot and hope its the right step? well, you won't ever know unless you try. keep the lines of communication open, no matter what happens keep talking. try not to worry so much. if its meant to be it will happen, when you both meet others whom are right for you. it may take awhile or it might happen rather quickly, keep talking about everything, and ask your wife to do the same. when your not even trying, its amazing how much natural compersion is already happening, just keep your eyes open to everything, your probably already feeling alot of compersion and just haven't realized it. just take it as fast or slow as you need to, and don't let anyone force you into more or less then you want. lots of luck