You could write a script for this.
Install On Timer script can schedule a script to fire every hour and the same step can be used to halt the repeat interval once all emails are sent.
You can use a loop and some scripting to send the emails in 750 record batches.
Thanks for your suggestion. We have someone who does the script writing for our FMP database. We've asked him to look into this and he says he can do it. Looks like we'll have a solution.