Vows such as these are likened to a clay pot, once they are broken there is not much you can do to fix it.
Hope you don't mind me picking one line out of your (very fine) post.
It might be reasonable for a person to ask,
"so, if I break a vow, why can't I just take it again later and keep it the next time around?"
and conceivably, I think it would be possible, and a good thing,
but it wouldn't alter the fact of breaking the vow the first time.
But keep in mind, nobody is (or perhaps very few people are) perfect.
My understanding is that truly breaking a vow "all the way" has three parts:
1. The willful intention to break the vow (on purpose)
2. The act of breaking the vow
3. A sense of rejoice in having broken the vow,
meaning also that there is no remorse,
and one looks forward to doing it again.
along with this one can include gladness in the result of having broken the vow
(for example, if you killed an enemy), and so on.
So, breaking a vow is both a pass/fail thing and at the same time
something that can be assessed in gradual degrees. It is both.
But I think the point is intention.
So, somebody in their 20's might take the vow with all sincerity, but let's face it, for many people these are the partying years in one's life. So, it is much harder to say, keep a vow not to drink or smoke pot especially if your friends are doing it.
probably easier if you have become a monk and live with a bunch of other monks.
But if you think about the precepts the way people think about wedding vows,
one the one hand, many people get married "too early" and often break their wedding vows,
and maybe the marriage breaks up or stays together, but the "damage is done"
...you can't go back in taime and say it didn't happen. So, it is a sort of scar that you keep with you.
Maybe if you are clever, you will learn from this scar.
Then, it is quite possible that the next time you get married, things will turn out differently
because you understand the seriousness of the whole situation a little bit better.
Ask your teacher if it is possible to take precepts a second time.
The problem is, breaking vows can become habit-forming.
"nothing happened to me the first time, so what's the big deal this time?"
The answer might very well be NO.
but maybe yes.
I don't know.
Taking a vow never to do a particular action ever, ever again is a heavy thing and difficult to keep.
That is precisely why