You shouldn't have any real issues running CS4 on Snow Leopard... I have done so successfully since day 1 of the Snow Leopard release. Also, you shouldn't have to even explicitly run it in 32 bit... because Snow Leopard will run it just as Leopard ran the Carbon app. While Carbon is completely compatible with Leopard, it's core doesn't allow the operating system to "see" it as 64 bit. So even though a developer could, say, write a 64 bit app in Carbon, it will not get recognized as such. But that does not mean that it is incompatible.
As far as the bug goes you mention, the Extension Manager has been buggy on all Apple machine and I think somebody at Adobe is crossing their wires in making it sound as if it is because of Snow Leopard. The reality is that the extension manager has been buggy on all Apple OSX systems. I remember it having the same "cache" problem in Tiger, then Leopard, and Snow Leopard. Adobe has admitted that they are the culprit on this and have made mention that it would be fixed upon the release of CS5 (or whatever they may rebrand it to). The only other benefit is that the entire CS5 suite will be rewritten in Cocoa completely. While I am not sure how much better Flash and Dreamweaver will actually perform, I am told this will really fix the issues that Fireworks has had with instability on the Mac - which would be quite welcome. While I love Photoshop, it certainly does not compress images with the efficiency that Fireworks does.
As far as your WebAssist extensions, they all should work fine with maybe the exception of Google maps... I have yet to really test it. I would tackle each issue one at a time and if needed post the issue in the appropriate extension forum and the WA engineers will open a support ticket for you if needed. I am positive you will be able to get everything resolved on here rather quickly and be developing with no issues.