Are you using the free version?
If yes, it should be possible to bypass the Play Store completely. Ideally, install the older FDroid version, this will certainly isolate the app. The current version then could stay, you would need to copy the files from the OsmAnd folder to avoid downloading the maps again.
You have to allow installing apks from outside of Play Store and maybe even disable checking of installed apps in Play Store. After every Play Store update, you have to check its settings again - the last few versions keep disabling my settings. Your problem otherwise is that you keep fighting the system (the Play Store / Google settings). With current Android / Play Store this is not easy - and is perhaps even impossible - to win.