Which Level Is Last For Non-Subscribers? I just finished Prime Pathing and no other quests are appearing after it.
Prime Pathing is indeed the current last-level for Non-Subscribers.
But every Wednesday new levels will be published. It is your bad luck that the official release for Prime pathing is today and the rest are subscriber-levels, but stay tuned for next week (I happened to have some insight in what will be released).
If you want even more levels or test subscriber levels before they become subscriber-only try joining the Adventurer-Mailing list. You can test new levels one week before they hit the public. As you played through the glacier you are easily overequipped, so you can do these levels as simple or hard as you desire.
More often than not you will find that you engineer an over complicated solution because you can. Take it as training-possibility.