Hi,
There are many angles to approach the problem you propose, therefore my answer will contain my personal preference on what to do:
1) CCSv5 is perfectly stable when installed with all device families, therefore the ARM and DSP toolsets coexist perfectly. However, if your existing CCSv5 install with DSP support is critical for your current project, or you need to keep this development environment frozen for future maintenance, then I would install an additional copy of CCSv5 with the ARM support and in a different directory (also use a different workspace). This way you can keep both development environments absolutely isolated. I don't understand your question about the AM335x SDK - this and CCS are completely different products.
2) From the debugging standpoint there is no problem, given the CCS can access your target board via GDB or JTAG. However, to have access to the source code and have full symbolic debugging, you must have access to the source files in your Windows environment (usually SMB is the type of service that allows that). To build code, however, it becomes much more complex, as the AM335x SDK only installs in Linux and the build tools are tied to this OS. In other words, it could be done but I would not steer away from the original development environment and waste time in trying to adapt my build system. Regarding Android, I don't know it very well to make an educated guess.
Hope this helps,
Rafael