I have a custom not to reply to individuals, but since you seem to be a very learned young man, and your mentschlichkeit is unusually remarkable for this site, I’ll make an exception.
1. I do not advocate someone foresaking their minhag. However, if someone did not grow up with this minhag, I feel there is no reason to abide by it.
2. The main question in this sugya is whether one needs to have a hatarah in order to change their minhag, as the minhag becomes a neder. This question arises when the minhag is not mi’ikar hadin (that is, some say it is assur al pi din), but it is done for chumra or for prishus and the like.
3. One opinion is that this hatarah must be done. In that case, someone who totally separates fish and meat and wants to stop this practice would need a hatarah. So be it.
3. Another opinion is that if the minhag proves to have been a “ta’us”, no hatarah is necessary.
4. In my opinion, any custom which was thought to have been a sakanah and is now known not to be, can be considered a ta’us and one may decide on his own to stop the practice. Fish and meat would be considered to be in this category. It is not assur al pi din to use the same fork or plate for fish and meat. Rather, it was thought to be a sakanah, but it is not. Mentioning “spiritual sakanos” is a flight of fancy and I don’t consider that suggestion seriously.
In summary, anyone who practices this minhag and is comfortable with it should continue to do so. Anyone who did not practice this minhag need not begin to. Anyone who wants to stop practicing this minhag, or finds themselves in a situation where they cannot, may do so without a hatarah.