You have an unrelated bug somewhere ... files of these sizes are inconsequential, and nothing should cause Apache to “grind to a halt and die.”   Therefore, I cordially suggest that you are chasing a red herring right now.   You have a bug somewhere in your code.

Set up a simple way to invoke “the guts of the thing” directly from the command-line with some existing disk file (representing the already successfully-received upload content) as its input. Use this to find the hole in the algorithm which is most likely an endless (or near-endless) loop.   Factor both the Web and Catalyst out of your investigation, as it is sufficiently unreasonable that either of these are the source of your problem.   (In my experience, it’s probably going to turn out to be “a friggin’ line of code or three, obvious when you see it,” and you’re gonna slap your forehead and say, “Doh!!”)