How can I migrate my openings from Chess Position Trainer to another database when the pgn too large to import? I have used Chess Position Trainer for years.  I now only play "postal" chess and no longer memorize openings.  Also chess position trainer is the only application I have the requires windows and I would like to stop using windows.  

Some of my openings seem to be too large to import.  I have tried importing into chess tempo, ChessBase, and a local HIARCS chess explorer and they all error on import for large openings.

Chess Position Trainer supports exporting as a single PGN or a game per variation.  exporting as a game per variation scales better but still does not work for my largest openings such as King's Indian as black.  

How can I migrate my openings from Chess Position Trainer to another database?

I am using Chess Position Trainer 5.04

My preference was to use Chess Tempo but would be happy for suggestions of other chess database software to try, either browser based or local for my mac.
You can export subsets of your tree of moves or export each variation as an individual game within the same file. Acording to the manual: "You can export an opening or topic as PGN file which then can be imported by many other chess programs. Several options let you configure the export to your preferences. The  most importantone might be the option to export as “One Game” or “One  Game  per  Variation” (the latter is only available for openings).