1. It hurts so bad to see him touch her, kiss her, show physical love...what do I do to overcome this pain?
I went through this too with TruckrPete and Mr. A. Those thoughts cannot really be overcome easily. Ultimately it took a lot of communication on our part to handle it. I set ground rules, initially (they've been lifted now) that I did not want to see physical contact. Eventually I overcame these feelings by communicating when I was upset, what specifically upset me, and TP was responsive to my feelings; and that's the key if your husband does not want to take your feelings into account then he's selfish.
That being said part of the hurt you are feeling could be coming from being betrayed prior to your discussion of Poly; because frankly, that's what your husband did. It's one with thing to call it poly after the fact but in reality it was just bad monogamy. Is he saying he's poly because he is or because he got caught cheating?
2. I have yet to experience "knowing that he is with her" that they are together while I am at home, and that they are having sex....loving each other, being physical with each other....I know it is going to hurt....what do I do about that?
I had terrible anxiety over TP and Mr. A being together and me sitting at home; at one point I came close to a full blown panic attack. Again, it was communication that I did not want to know details other than they were out, and that's something that's still in effect today.
It's hard to pinpoint when or really how I overcame that feeling, but I think it was just that eventually I realized that there's no division of love lessening TP's love for me and she loves me just as much (actually more since I gave her the green light for poly) and also that she will eventually come home. Part of it was that I met and became friends with Mr. A, that helped immensely because he was not some guy trying to steal my wife (then fiancÚ) but someone who was respectful of our relationship and that there would be an adjustment period.
The best advice I can give you, since I have been through it, is that you need to set hard guidelines of your needs from this poly relationship; that is what restrictions will make you comfortable enough that you are not hurting. It's on your husband (and subsequently the girlfriend*) to allow you time to adjust, if he's not willing to see it from your perspective and just plows ahead in his relationship, you need to reevaluate his respect for you because if that's the case you and your feelings don't mean much to him.
As for your feelings of inadequacy that you are not enough for him, I cannot speak to his motives, but I can say that this might not be the case. I had to discuss this at length with TP because I was constantly making a direct comparison to Mr. A. That happened, and as I eventually realized, Mr A and I bring decidedly different things into TP's life; we are similar but different in ways that makes TP love us.
I recommend having a long discussion with him about his girlfriend and their relationship; touch on your needs for restrictions to make you comfortable, his reasons for wanting poly (see above re: getting caught) and what he can do for you to show you that you are not inadequate. All that being said though, you need to realize that some of the work has to come from you, I had to work on my jealousy and insecurities too.
Polyamory is wrong! It's Multiamory or Polyphilia. Mixing Greek and Latin roots? That's wrong.