We must be always be online at the same time because we're both on the west coast.
Here's what I think - there is a difference between your husband not being an active particpant in the marriage (which is what is happening) now and actively wanting a divorce (which may or may not hapen). Honestly, there probably are days when he thinks he wants a divorce, but probably not all days - I just don't think thats human nature especially with an 18 year relationship that appears to have started in your teens.
I know this is hard. I'm right there with you. I've seen several posters caution against timelines and I understand the rationale, but I've found it helpful to think that I really am going to have no expectations for improvement until at least the end of the year - other than the two of us being effective co parents. I assume that if there is no improvement at that point, it will have become more of a habit of thought and will be easier to maintain then.
A separation is a big deal. I don't think any WAS is really going to know or resolve their thoughts in a period of a few months. Obviously, my sitch is a little more dire (OW and husband has affirmatively stated he wants D, although he was very willing to wait 6 months)- and I have accepted that if the situation does turnaround, if my H realizes what he is trhowing a way- its probably going to take him a long time. In some ways, I think my situation is easier, because its pretty easy not to mind read right now - and I feel like I have no where to go but up. It also makes it easier to focus on GAL, which really is starting to kick in and help me.
I think you need to embrace this and stop tortuing yourself over every interaction (Honestly- I talk a good game but I would have been thrown by a vasectomy announcement as well).
Your husband probably has no idea what he wants and it could easily change hour by hour, day by day. He is in some sort of crisis right now. Accept that in regards to your marriage, he is not stable right now and when you are reading into things, wondering what he is doing it is only hurting you.
You seem like such a charismatic person with such a lot to give - focus all that wonderful energy on something besides H for awhile.