How can I make the Music App play only downloaded music in my iPhone?

I have an iPhone I keep in my car permanently. I also have an Apple Music subscription. I have configured the Music app so that a specific playlist is downloaded to the device. This works correctly - when I add a song to the playlist via my MacBook it automatically downloads to the playlist on the phone. However, I have 2 problems which I am unable to resolve or find an answer to.

1. Music never continues from where I left off. If I leave the vehicle for more than about 10 minutes it seems to forget where I was and rather than continuing with the playlist just does whatever it likes.
2. Having returned to my car and the playlist not continuing as above, the Music app then attempts to play songs from my library that are not downloaded to the device, resulting in silence.

Question. How can I make the Music app play only downloaded music and how can I make it play the playlist I ask it to like my iPod did with iTunes for 15 years without any issues. Do I really have to cancel Apple Music and go to Spotify to get such a simple feature? I've seen this question on this forum, with hundreds of "Me Too" but nobody has answered.

[Re-Titled by Moderator]