You don’t have to obfuscate the code to do anything else you mention. You should be able to run ProGuard over the output of Processing somehow - it’s all Java bytecode! However, you have to make sure to specifically exclude the Processing libs from the process - your users have the right to take apart your plugin and change the Processing and other libraries it’s using. If you don’t like that fact, use something else! 
All obfuscation is likely to do for you is make problems that you don’t need for your use case.
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