We are sorry to hear you had a rough outing. There is a lot here but we will attempt to address them all. In the interest of having the response be usable for future searchers it is much better to post single topic issues one by one.
1. Yes, this is by design. We pay for every tile that is saved. Most operation is done with some internet connectivity so it defaults to using the standard Apple basemap, which is free. Most of the time users will know if they are going to be operating offline and it is their responsibility to make sure things are properly loaded ahead of time. We always recommend checking that all of your data is present before leaving for the field anyway. Some subscription tiers do not have access to saving the basemap data anyway.
2. Make sure all other drone related apps are fully closed. If it doesn't connect you can unplug and replug the cable to trigger a reconnection. If that doesn't work check your cable for bad connection. If that doesn't work reboot the aircraft and remote. If that doesn't work fully close and restart Map Pilot Pro.
3. This is a known issue with Virtual Stick flight that happens because of a incomplete disconnection and reconnection process. Likely related to issue #2. We have tried to get rid of it but it is part of an iOS bug that DJI won't be fixing so we have to do all sorts of stuff to work around it. It only affects iOS with Virtual Stick devices. Make sure you are using the latest version.
4. We try to keep any forward progress but in the case of a loss of this you can restart at any corner waypoint by tapping on it while the blue verification line is showing.
