Okay
Okay, that is a very cool quest. And your friends are very foolhardy to not spend the time with you.
But first thing I'd do is cast Detect Magic and utilize that Spellcraft skill. It'd suck to waste 2 years at the wrong glade.
If there're faeries in the area, you've got to get on their good side. Apparently even animals would develop weird abilities, so you'll need help. Since you're Good, smart, more charming than the average joe, skilled in the way of Fey, and speak the language, you should be able to find and win allies.
That's what I'd do if I were your character. No way would I attempt to go it alone. I mean, you've got to assume that the local Fey know of the place--why bother to hide? Instead, cross your fingers and try to establish rapport. Maybe your skills and magical abilities can help them determine the nature of the magic field.
Another thing to consider: your familiar will most likely get a magical boost as well. Have you chosen a familiar? What is it? I suggest an owl, becuase of its sharp vision, ability to fly in a forest (as opposed to just above it), ability to bring you food, and nocturnal sleep cycle (can watch while you sleep).
The other choice would be a raccoon. Raccoons hunt small critters, but they also forage. And bonus: a raccoon can help you dig.
I like your river cave idea, but I'd seriously consider expanding it. Ideally, you'll have enough room that you can completely yourself in for the winter. You can always dig down to the water table for water (a crude well), and you can get stones from the river (no need to dig them out of the dirt or carve from solid rock). The wall will protect you from hungry predators, keep out the wind, and help keep you warm. Just make sure to keep one part of your tunnel system cold for food storage. Use those sleep spells (+ coup de grace) to build up a supply of meat, and use your familiar and your own abilities to store up a supply of nuts and tubers. With minimal exertion and the warmth of the cave (thanks to prestidigitation), you should be able to last the winter. But holy cow, will you be bored out of your mind.
If I was your DM, I'd give you a penalty of -1 to Cha for every 3 months spent in isolation, plus a Will save or -1 to Wis (both recoverable through a month or so of re-socialization).
Good luck.
PS: when you do get your fancy powers, consider blasting your so-called "friends" to smithereens.