If you go to book -> stats -> unlocks, at the bottom are options to copy achievements and load achievements. You might be able to use that to copy from Android and load on PC.
Purchasing for PC gives a file you can load on Android. Sadly, I don't believe there's any way to apply your purchase from the Play store to Itch.io. You will need to purchase from Itch.io to gain access to the PC version, though you do get all other versions with it too.