The 5 adventurer group doesn't give more xp. There is basically no real bad choice from a gameplay point of view, so feel free to role play your way as you did.
The "no hint" and open approach is actually a feature and not a bug. As for the turn by turn combat, this is to revive the old crpg experience. Still I must say some puzzle and quest are unfair at time and require solution that might be seen as cheesing. But on average, resolving a quest is more "rewarding" this way.
As for your problem, a lot of xp can be acquired without even leaving the town. Since you did the lighthouse, you might want to report it to aureus for a lot of xp.
