Your fears about the smartphone are not unfounded. If you take a regular smartphone with you as you go about your day, it will collect a ridiculous amount of data against you. Even without Internet it will cache the data and transmit it once it has signal. Only way to stop it is to install a custom ROM.
Keep in mind that even a dumb phone can track you. If it’s connected to the cell tower then the telecom companies know your location and may share that with others. Also, calls and texts are not encrypted on a dumb phone and are probably being intercepted.
See if you can trade in your new cell phone for a Google Pixel and install GrapheneOS. That is currently the best privacy ROM. You can use this like a dumb phone and it will track you no more than a dumb phone could. To prevent tracking from cell towers, you can put it in airplane mode and use messaging apps over WiFi.
Wrong. I have nearly died on several occasions because I didn’t wait the required 30 minutes. The second time I waited 28 minutes because I miscounted and that was all it took to earn me a trip to the ER.