LOB in frequently queried table or separate table
is it better to store this column in a separate table with 1:1 relationship to the FinTrans table, or shall I just leave the column where it is?


Leave it. That's tiny, and not worth adding complexity.  Also, even if both the table and the LOBs were larger, the answer is still to leave it.  Large LOBs will be moved off of the row, and you can set a configuration option for all the LOBs to be stored off-row.  You can also configure the table for the LOBs to be stored on a separate filegroup.  So there's no reason to change the logical model here.  

See:


  large value types out of row 
  
  1 = varchar(max), nvarchar(max),
  varbinary(max), xml and large user-defined type (UDT) columns in the
  table are stored out of row, with a 16-byte pointer to the root.
  
  0 = varchar(max), nvarchar(max), varbinary(max), xml and large UDT
  values are stored directly in the data row, up to a limit of 8000
  bytes and as long as the value can fit in the record. If the value
  does not fit in the record, a pointer is stored in-row and the rest is
  stored out of row in the LOB storage space. 0 is the default value.


From sp_tableoption