1. The most important perk: awakened. This allows you to get a soul crystal every time you level up. Make sure this is the first perk you get! The first level of focused is very useful in my opinion, it prevents you from losing track of your opponent's moves as easily. You'll want to invest as much points as possible in strength, endurance and agility, with your base perception at 5-6 (you'll get perception boost from the helmet in second town too). If you have leftover perk points after all of that, Versatile is nice to have. Don't be afraid to save up perk points to get the extra strength/endurance/agility boost!
2. Yes, there are two additional maps. I won't say anything about them, you can figure it out yourself :).
3. You should have at least 1 perk point in strength and endurance, perception 8 if you can, agility as high as possible. Get the heels and helm and upgrade them with soul crystals to get even more stat bonus. Get the gauntlets of strength from the giant and use crystals on that too. Make sure you use the gem at the witch's cottage to defeat the quetzal goddess and try to return to town with the altar afterwards. If you eavesdrop again you will receive 300 gold, which you can use to buy food and optionally the full plate (otherwise you need an insanely high agility stat to steal it). If possible, buy the town scroll, just to have a way back if you run out of food or anything.