Unrelated to this specific post, but on the subject of Fil-C and Programs That Work[0].

Let's say I compile curl using Fil-C, and later an exploitable memory bug is found in curl. The implication here is that my fil-c-compiled curl will crash safely, rather than be able to be exploited? And the "cost" to me is that my curl executable will be slower than the standard one?

0: https://fil-c.org/programs_that_work

Correct.