First off, yes. There are a few:
- "I Love Native"
- StripPPC (strips only PPC)
- Strip68K (counter-app to StripPPC, it strips 68K)
There might be a few others but I can't remember their names immediately.
It is worth noting that 68K Macs load programs in segments, unlike PowerPC Macs which load programs in large chunks. Usually only the code needed to perform a particular task is loaded into memory at any one time. That is why PowerPC Macs consume so much more RAM than 68K Macs. They always have more code in memory (you can turn on Virtual Memory and reduce memory pressure a bit, however). So stripping PowerPC code from FAT binaries will save you disk space but I am not sure you will see a huge amount of performance increase since I can't imagine that any PowerPC segment code would ever be loaded on a 68K Mac, FAT binary or not. (This is not true of PowerPC Macs and 68K code.)
As for running 7.5.x on a '030 … eh. It's not very pleasant. I've found that for me personally I get more enjoyment out of my vintage Macs if I stick as close as possible to the "shipping OS" as I can. That way the machine always performs like it did when it was brand new. Pushing an old Mac to the latest supported OS often just makes the machine feel slow and clumsy.