For unsigned BIGINT items, I’d probably use a CHAR(8) column in my tables. There’s nothing that can be done by DB2 for these values; all must be done by programs, so the database doesn’t need to know anything about the contents.
I don’t know the date format for those journal entries. My first guess would be that they are system date/timestamp fields since they’re 8-bytes in length. I would first try the Convert Date and Time Format (QWCCVTDT) API to see if they converted with an input type of *DTS. Again, store them as CHAR(8) in any tables. The numeric values are essentially meaningless; treat them as binary (or hex) values.
If I saw values for remote address that weren’t meaningful, I’d first check the value in the Address family (JOADF) field in the returned entry. What value do you get in that field?