I'd like to make commercial software on Python.

ソースDo I have to disclose all the source code?

No, you don't need to disclose it.

This does not apply to using GPL-licensed modules.

逆Is it impossible to compile without decompiling?

It's impossible in all languages, not just Pyhton.

You can use Cython or pyminifier to make analysis a little harder.

PI am using several modules such as Pandas, but is there a knack for compiling them into exe format?

Here are some important points to note when using the main libraries.

http://www.py2exe.org/index.cgi/WorkingWithVariousPackagesAndModules

ソースDo I have to disclose all the source code?

You don't need to do this unless you have a license, such as your library.

逆Is it impossible to compile without decompiling?
③I am using several modules such as Pandas, but is there a trick to compile them into exe format?

There are other ways besides py2exe to compile Python-created projects, including dependent libraries.See "How do I compile Python programs into executable binaries?".

I have the impression that Python doesn't have that much demand for code-keeping, and that tools aren't developing very well.I think we can make reverse engineering difficult by using obfuscation and encryption.See "How do I protect Python code?" (not just the top answer, but other answers may be helpful).