Thank you for your post, and I apologize for the late reply.
Although I am unable to replicate the issue, the recursive calculation should stop after several thousand iterations. Recursive functions are useful for figuring out estimates and different mathematical functions. In your case, you may want to use Set Field script step to grab the results of the ExecuteSQL statement so you it only calculates once.
Let me know if you need additional clarification.
50,000 is the limit of recursions.
Hmm, I'm not entirely sure it would have stopped if I hadn't force-quit. I was waiting for a number of minutes, and the filesize was pretty enormous by the time I was done. I'm in no hurry to test it out again, but anyone who wants to inflict a force-quit on their FMP is free to try my steps listed above. It's not complicated to set up, and you don't need External SQL Sources in place or anything. It's just a mundane use of the new ExecuteSQL function to find multiple columns in a local FileMaker table.
Edit: But, yes, as TSGal suggested, making it something other than a live calculation field might be warranted.