Sorry for delay. Thanks for more detail, it does make it sound like there are many positive parts to your relationship. I will try and answer some of your questions.
I think (with or without Freud), sexual tension can cause mood swings and thoughts can build in the mind about what is happening. These thoughts MAY be fundementally based upon distorted thinking - for example, "my husband cannot satisfy me, so I am entitled to gain sexual gratification elsewhere". Sometimes people pick up what are called 'schemas' - ways of looking at the world, which colours their perspective. You've heard of rose-tinted glasses where people always see the world as beautiful? Well, sometimes, (often through no fault of their own) people view the world in a certain way, for example, My needs should always be fulfilled, OR I deserve..... OR I am entitled to, etc. etc. and this can affect how the person lives because this is their belief, driving their world. BUT this belief may be so strong that it takes over - and can be sought after regardless of anyone else's pain or suffering. Does that make sense? I am wondering if your wife sees herself in this way somehow and only you and her will know that.
I'm sorry, I'm not sure that I buy all this sexual stuff that she is telling you - its not the toys she has to like - it's what you do to her with them she is supposed to enjoy - (that's not supposed to sound as obvious as it does) - and I suppose, yes, it makes me suspect her motive and I will explain why. Yes, there are emotional sexual needs, but she is putting her sexual needs above the importance of your general well being. A friend once said to me that she doesn't believe that compromise is always good - if you like life to be blue and your partner prefers it to be red, to always compromise and live a purple life suits neither. However, if you live a comfortable purple, with blue days and red days, then everyone is happy. And I agree with this - it's about accepting who you have married for who they are. But should your wife have her red days if it sends you into darkness? My advice would be 'no' because fundamentally she is not showing that she cares about your general welfare. You cannot expect someone to like your hobby, to sit and fish all day, to play golf, to bake cakes, etc. etc. but these (generally) do not cause grief to a partner. To have sex with someone else is outside the boundaries of a happy marriage if it isn't agreed and accepted by both partners. And I would say that even if it has been agreed, and then doesn't work because it causes distress, then the primary concern of the wife (in your case) is to think about the happiness of her husband, not her sexual needs, which could be fuelled by the underlying belief (as above) and in my opinion, is selfish (thinking only of oneself as opposed to the welfare of others).
My judgment on this may be wrong, but I would suggest that you are careful of what appears to make your relationship seem 'stronger' - you feel jealous, she returns - you (perhaps) feel grateful and happy that she has returned - that's NOT love - that's you being grateful that she has given you some time, but she is your WIFE, is she not supposed to give you her time? Which goes back to the marriage agreement in the very beginning.
Lastly, your interpretation of EMDR is correct - it is a controlled desensitisation until the emotion is released. Or you could try EFT - emotional freedom technique. This is very simple and you can do it yourself. Using your fingers on your right hand, tap on the side of your palm on your left hand, between the base of your little finger and your wrist and say to yourself 5 times, "Even though I have a small penis, I am a good man and I deserve commitment". Change over your hands (tap the edge of your right hand using your left fingers) and say 5 times, "even though I love my wife, I can stand up for myself". You may feel your body tingle - this is the release of the energy that is holding the negative beliefs inside. You can find lots more information and videos to help you at http://www.tapping.com/ I haven't given you this advice to cause arguments, it needs to be pondered carefully by yourself. I would imagine if you ask your wife about it directly, she would deny this, but to be fair to her, she may not even recognise what she is doing, due to distorted beliefs. Have a look at the rest of her life - does she always get what she wants at any price or cost to others? What is her reaction if she cannot get what she wants? How does she interact with parents, siblings? Has there been big fall outs and if so, why? I would suggest that you give yourself some time to think it all through and make some decisions for yourself, about yourself, before you discuss it with her. If you have found this answer valuable, please press accept. Happy to reply. With Best Wishes, Sarah