Hi Kyle,
1. There is a custom code you can try, when using the index table engine. It is very far from a good solution, but it should work for most cases. You will have to put this into the functions.php file in your theme directory, copied from line 4. Make sure to have a back-up first. Then re-creating the index table will trigger this function.
2. Well, there is an export/import function on the synonyms tab, but that is more for internal use. You would have to convert the file into the correct format (JSON).
It might be easier to look at the asp_synonyms database table, and do the import there directly.
I am not sure about the performance implications though, as it may get very very slow. Each keyword has to be compared to that table, and it is done in PHP for the best possible speed. There is a hard limit set in the code to allow 15000 synonyms total, but even that number could potentially cause a failure. It is very much server dependend – if the PHP memory limit is high enough (512M+), it could actually work.