Your Strength was listed as 31 out of 38. You can invest 7 more points. If you continue to use melee, I would consider Constitution and Dexterity. Don't fret about choosing one or the other. You can respec your skills and stats at any time at the quick change station. It costs 10% of your current gold to respec.
A Walk to Dismember was a rather short but memorable quest with a decent reward. Take this if you like being bitten and insulted. Raiders of the Lost Shark is a fetch quest with a bunch of loot at the end. It can give you an excuse to wander out in areas to find some collectibles. Give the pearls to Chumberlee. The Trials of Crooked-Eye Phil is the central quest of its side area. It is longer and has a climactic finish. Twenty Thousand Years Under the Sea has less action but has a wholesome ending. Walk the Stalk is the central quest of its side area. It is both bizarre and awesome with one of my favorite bosses at the end. It is in a side area with a few other side quests too. Check the Overworld for additional quests and dungeons. Some of the shrines are ready to be completed.
1:30:46 This is where you swapped out your shield with one that was less than half the size. That is why your shield felt weak during the obelisk in part 9.
There are no hidden quests in unexplored areas. All quests in an area will be listed in the progress UI. However, there are TONS of stuff to find and you should definitely explore a bit to find them. Even after all of the collectibles (loot dice, marbles, poetry pages, rune switches, and obelisks), there are chests full of loot and some lore scrolls to find.
15:10 For this rune puzzle, you would need to go around the other side of that building. You can begin running towards the first rune before it appears.
