You ended your letter by saying if there's no sperm discharge without ejaculation then it's time for you to leave. What I really think you're saying is that if the discharge you see indicates that he's ejaculated, then he must be cheating on you.
Rather than focus on understanding the male plumbing, I think we should talk about how you feel. Clearly you don't trust your husband and with good reason. Just because this woman left for Indonesia doesn't mean your problems have gone away. An affair is a symptom that something is wrong in the marriage. What is wrong isn't going to go away just because the women he had an affair with has left. I guess you know this on some level and that 's why you're obsessing about his briefs.
Talk to him and begin to identify what's not working in the marriage. The key here is for you to avoid the temptation to play the wronged or injured party, the victim of his infidelities. If you're going to save the marriage, you will need to take ownership of your part of its destruction. I'm not saying he behaved properly by expressing his discontent with the marriage by cheating. That wasn't ideal. But if you're going to move forward you're going to need to find out what you did to drive him away from you.
Having the courage to ask is the first step toward healing. When he tells you what was missing for him and/or what you have been doing that he doesn't like; or what you've not been doing that he needs, you will be at an important crossroad. You can either work to respond to him and make the marriage work for him or you can choose to stay the same and have him cheat on you some more and/or end the relationship.
Keep in mind, if you resist stretching and growing and you just end the relationship, you will find yourself at this same impasse in your next relationship. So, why not take care of business now rather than be forced to take care of it later with your next partner.
As for your husband, he needs to realize that he's been expressing a lot of anger toward you by cheating. Instead of cheating, he needs to commit to talking with you whenever you say or do something that angers him. In exchange, you must promise to listen and do your best to be responsive to him. In a nutshell, this is how you will save the marriage.
If you need additional help, my book, Till Death Do Us Part (Unless I Kill You First) will guide you step-by-step on how to listen and understand each other, even when you're mad. The book (and my Personality Profile consultation, which is included in every Action Plan) will also help you identify and heal the early wounds that you both have brought into the marriage. It is these unrecognized and unhealed wounds that act like a cancer and gradually erode a marriage.