Holy shit, I actually made it work myself. If any other amateur is interested, here is how to do it:
1. Download https://drive.google.com/uc?id=1VmbAz2FTD9oLIhi7_drzCEPiTFcR-CW9 and unzip it and install it.
2. Download the Pac-Man Battle Royale-v2.7z (link in the first post in this thread) and unzip.
3. Download PacMuseum.NoobDiff and also NoobPatcher http://www.emuline.org/topic/1251-utilitaires-pour-debutants-noob-tools/
4. Start NoobPatcher. When starting NoobPatcher, you will get the option to select a file. Select the original PACmuseum.exe file (this file is normally located at C:/Program (x86)/PAC-MAN MUSEUM). After that, you get the option to select a second file. Choose the PacMuseum.noobdiff file that you previously downloaded. NoobPatcher will now say "Patching successful or something like that".
5. Now click on PACMuseum-patched.exe that has just been created in the PAC-MAN MUSEUM folder. The game should now start.
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6. To get your controllers working in the game, start by downloading X360ce from https://www.x360ce.com/. Very important! It has to be the version made for 32 bit games.
7. Unzip the folder you have just downloaded, called x360ce_x86.
8. Start x360ce and let it create xinput1_3.dll.
8. Now make 3 copies of your xinput1_3.dll file in the same folder (copy and paste thrice in the same folder). Name the first xinput1_1.dll, the second xinput1_2.dll, and the last one xinput9_1_0.dll. Give administrator permission when needed.
9. Copy all the files in the x360ce_x86 folder to the PAC-MAN MUSEUM folder.
10. Start x360ce from its new location. Above the controller pictures there is a horizontal row where you can choose which game to make the controller settings for. Now you want to choose PACMuseum-patched.exe in the drop-down meny.
11. Remember to save your button settings. Then close down x360ce.
12. Now start PACMuseum-patched.exe and hopefully your controllers will work with the game!
