Welcome to the site. I'll try to contribute what I can.
1) The spanking desire never dissipates. A while back someone posted something on another site, but I've forgotten who and can't quote the person directly. What they said was, "Interest in sex wanes over time, but spanking is forever." This sums up spankos very nicely. Frankly, if you did connect with someone, you'd likely go into "newbie frenzy" and wouldn't be able to get enough for a while, as opposed to making it wane.
2) I'm in a similar situation, except my kid is grown. I've done four spanking sessions so far this year. I still think about it almost daily, and the fact that I work with a woman who gives off incredible amounts of spanko vibe tends to help keep it in my thoughts. Of course, I never suppressed this urge, so for me a few sessions a year is enough. Or so I tell myself. If it weren't for the kid and my 86-year-old mother, I'd probably be doing four sessions a month, not a year. And I've been doing this for over 30 years. This is a long-winded way of saying that one session a month won't stop this from permeating your thoughts. It would normalize it for you, over time at least, but it wouldn't stop it. Short-term it would probably only intensify, and then wane over time. Once it starts to wane, and becomes "normalized," you'd then be able to balance it out in conjunction with the rest of your life. More on this in my next answer.
3) For me there isn't "urge" anymore, but that's relative to the fact that I have been doing this my whole adult life. The desire is always there, sure. That never goes away. But the desire is always there to get out with my camera and do some photography too. Bad weather or other commitments sometimes makes me curb that desire to get some photography in and given that I've had a lot of real-life experience with spanking, I can likewise curb the desire for spanking play. This is because I've normalized the kink within the greater context of my life, which in turn makes it easier to balance off in relation to everything else. That takes time, though.
4) This is a tough one. In all honesty, Millennials and Gen-Z are going to be the litmus test for this. A small number of Gen-Xers made a semi-open relationship arrangement with a spanking partner and a vanilla spouse work, and I know of one, and only one, Boomer couple who pulled this off, but for every success story there were probably hundreds of failures. The two generations coming up behind mine are more open-minded, as a rule, where this sort of thing is concerned. If your wife is giving you the green light for platonic spanking play outside of the marriage, then I would encourage you to explore that, but you'll also need to open a separate discussion about how to navigate the minefield of an open relationship. There is going to be risk involved with this, and success is not guaranteed. The biggest problem in these situations is that non-spankos struggle with the concept of us doing this platonically. That theme frequently came up in the failed attempts of which I am aware, at least. Addressing this aspect might be the best starting point but be aware it will likely need regular reinforcement.
Can't help with your last question, as I can't relate to a desire to receive. I believe others here can speak to it though.
I hope this helps. You may find some answers overwhelming, and that's okay. Keep asking questions. We have a good crew here and tapping into our knowledge is free of charge. 🙂