It’s a principle in databases, and it applies here also, that a “key” should be nothing more or less than a record locator.   It ought not convey anything about the record being located; it should not be part of the data.   In this case, though, a hash value such as abc;def clearly is “a list of important values.”   Therefore, IMHO, it has absolutely no business being a hash-key.

If you find yourself wondering how long a hash-key value can be ... you are doing something very, very wrong.   :-)

This might be an excellent application for an SQLite database file.   Instead of busting the top off of your memory allotment, put the data into a special kind of file that is built for searching using SQL strings.   As long as you remember to use transactions so as to get lazy disk-writes, it is rugged and fast.