I understand what Dr. Talon was saying. I think he has a very valid point, which I believe you missed, MC.
What he is saying, essentially, is this: while it may seem rather obvious or easy to focus on the fact that your partner wants to date other people as the reason for your insecurity and jealousy, that would indeed be "self-deception" in the sense that insecurities and jealousies are covers for other feelings and ideas we have about ourselves that we would rather not look at. Sure, his dating is a "trigger" that brought your insecurity to the surface, but that means it was already there. For someone else who doesn't already have such insecurities, being in your situation would not trigger the same response. It is totally possible not to feel jealous or insecure about it. So, what is it about... for YOU?
Usually we have established core beliefs about ourselves that are not very kind. We might feel inept, ugly, unwanted, whatever, but those ideas have been in place since a very early age and just live inside us, influencing decisions we make, and so on. But we've learned to live with them without really being conscious of those beliefs we have about ourselves, like a battery that keeps us going that we don't have to pay much attention to. And we can be pretty happy for the most part until something happens...
And then it's like an avalanche. And we're suddenly enmeshed in these terribly uncomfortable feelings. We want to blame the thing that triggered it ("my partner wanting to date other people makes me feel this way") but that does not get to the root of the problem. "Forbidding" your partner to date will not really help to understand the jealousy and insecurity that lives inside you all the time. That is what Dr. Talon meant when he stated that making your partner take a break from dating others will not allow you to dig deeper and see where those feelings come from. It would just be a delaying tactic.
The real work will happen when you look at why you feel these things, separate from your partner's actions. What does it bring up in you? And why do you immerse yourself in those difficult feelings? It could be a sense that you are less than desirable, for example (not saying this is you, just a hypothesis). But where did that come from? Perhaps a boy rejected you in third grade and you still believe that there's something wrong with you because of that.
I know it sounds silly, but that's where these ideas we have about ourselves come from. I have a friend who always felt inept and clumsy, even though she is an amazing athlete, and she realized one day it all came from being yelled at when she was five years old that she couldn't walk the family's poodle. She was too young, of course, to walk the poodle but in her mind she translated that as she was lacking in ability. She believed she wasn't good enough to walk the poodle and internalized that belief. "I'm not good enough." As an adult, she would go out on the golf course, compete in tournaments, and win prizes, but couldn't enjoy them and never felt she deserved them because she still believed that she just wasn't good enough.
That is insecurity - it isn't rooted in reality. It's rooted in memory, incorrect assumptions, and self-limiting beliefs. As is jealousy. So, yeah, saying it is all because your partner wants to date others is deceiving yourself. You have to look at what's inside you for the answers to unraveling the jealousy and insecurity you feel. Now, once you know where this all comes from doesn't mean it instantly goes away. It will likely come up again, but when you understand its origins you can stop paying credence to it and then those insecurities no longer have power over you.
But Dr. Talon also stated: "If you've got a lot of other emotional issues you're working through, I think it's valid to ask for time to work through them before adding more emotional stuff to deal with. But, if life and your emotional state are good apart from this one issue, there will never be a better time to deal with it."
Here's another way to put it, using an example. I've heard people say, "I'm so bad at relationships, I'm going to take a break and not date anyone for a year, so I can get my act together." Sooo-o, what they're saying is that they want to get themselves ready for being in a relationship by not being in one. Logical? On one hand, sure, that person can take lots of time to meditate and go to therapy and get to know themselves, but on the other hand, it's a relationship that will teach them how to actually be in one. So, I think it's far better to go out there and date, as flawed as we feel we are, make mistakes, and even have our hearts broken, if we want to learn how to relate to people.
It's the same thing for you. While, sure, you can ask for a moratorium and go off and do all your figuring out about why you have such a hard time handling your partner wanting another, or you can meet the challenge head-on and deal with it in the moment while he is dating. Baby steps are okay, but holding on tightly so there is no movement at all is not progress for either of you in handling this kind of change to your relationship. Most of the time the best way to overcome such debilitating emotions is to meet them head-on and challenge them. You might find that you are not cut out for poly, or you might discover that polyamory is great for you. Or you could decide to split up, but why leave the relationship before putting as much effort into it as you possibly can? Why not try to understand what this stuff has brought up for you and how you can create something for both of you that is unique to you and fulfills your needs. You might want to pick up the classic book Feel the Fear and Do It Anyway by Susan Jeffers, and Codependency No More by Melody Beattie, for some good tools on handling your emotions and creating the kind of life you want.