I thought that there was a way to send messages to iMessage from an android phone. It might not be ideal for you, but compromising on a messenger app isn’t that bad.
As for maps: I would use Magic Earth on Android. The navigation is just as good as google maps. The interface to OsmAnd isn’t very appealing, so give Organic Maps a try as well. The only problem is that Android Auto doesn’t work with a degoogled phone with microG, and that’s a deal breaker for some. In the worst case, you can just install Google maps: Using a single google app on a degoogled phone is not really a big deal, especially if you don’t log in. Using the google maps PWA with a browser is probably safer. Google will know what you do in the app, but that is all.
In any case, there is a big difference with having a spouse switch to a degoogled phone, versus you having to deal with minor inconveniences with not having access to iCloud and other things. I would just do all of your apple stuff at home on your desktop (I am assuming that you have a macOS desktop…).