You need to separate your problems with your husband from your feelings for this other guy.
If your husband treated you the same way this other guy does, all would be sweetness and light, right? So, recognize that your feelings for this other guy are symptoms of the problems in your marriage. View it as a problem to be solved, by you, rather than looking for someone else to give you what you want.
Fact is, you don't know anything about this other man except the tiny bit you know from your occasional meetings, with the rest filled by a lot of fantasy. Any 'soul mate' feelings you have are being generated entirely by this fantasy. You barely know him as a remote work colleague, much less as a romantic partner and step-daddy.
As for 'how long' it takes for feelings to subside, I can't tell you. My situation is very different from yours. The relationships between my husband and our friend is an entirely different dynamic. As I said, what I CAN tell you is the common solution to this type of problem. I've already posted my advice on this.
You can PM if you like for more help, but this^ really covers it. You need to recognize the source of this issue, and its NOT that you've found your True Love in this other man. Its that you've come across some real relationships issues that you need to solve for yourself, rather than looking to someone else to fix them for you.
Good luck to you and your family.