After doing some reading and learning some of the differences between x86 and x64, this problem is making more sense to me.
https://www.gamedev.net/topic/678905-dx9-doubling-memory-usage-in-x64/
Some stuff takes up twice the amount of space between 32-bit and 64-bit applications (I guess that should have been obvious), but now I’m trying to figure out what exactly in the contentmanager is doing that. When I get a bit of free time I’ll toy around with it again. I wonder if it has anything to do with the scratchbuffer that they use?