Well, none of those questions are unusual and none of them are new. They have all been discussed here at great length by many posters that have come and gone. You are in good company here
I suggest you have a good long read with her. There are stickies to read for one, that will help you find books and websites that are interesting and favorites of members here. If you go to the search engine you will find a tag search option that is very useful in finding threads that will answer your numberous questions. I would suggest doing a tag search for "foundations" "lessons" "jealousy" "mono/poly" and whatever else comes up of interest. I would also suggest reading the numberous blogs in the lifestyles and blogs forum also as they will give you insight into how poly has worked for many different people.
Take a breath, take your time, keep talking as openly and honestly as you can to one another and catch up to your partner. She likely has been holding her nature in for some time. Give her a hug and tell her that you can't imagine how hard that would be for her to keep such a secret.
Its a hard road you have just started, but its not the end of the world and you will likely find, having committed to the work together, that your relationship is created into something more wonderful and connected than you ever imagined. I wish for you that you find what works best and makes you both have the healthiest and happiest lives you possibly can.