I managed to 'Fast Travel' out, I simply walked down the hill into the river, and it then let me 'Fast Travel'. I couldn't get back sadly, so I had to make a new save.
It is possible to get out of the location, but once you do, you can't go back in, you should just go to 'Novice' difficulty, It is the easiest one, and you start off the game with a Healing spell, why not use that, as everyone has magicka.
Alduin is easier than a Draugr Overlord, in my opinion. I fought him with plain steel armour, on Novice difficulty, it was just like fighting an Elder Dragon with Daedric Armour/Weapons. Even if it is still too hard, you have two options from there...
1) Make a new save, and get better, and more stuff before going there.
2) Keep trying until you succeed. You may die a lot, but you'll get there.
In my game, I have been only on Novice, and haven't died from any enemies, and I am a level 37. All my deaths are from falling.
As I was typing that above 'Death Sentence', I thought of another option...
3) Be better at gaming.
As I thought that 'Death Sentence' part was quite funny, I have chosen to give you one more option.
4) Rush it. If you rush it, you can still get past and go to [SPOILERS] Sovngarde.
I suggest not rushing it, as there is a Dragon Priest at the portal to Sovngarde.
He has a mask, this mask is unobtainable in any other way. So, if you want to get the Secret One, which can be found at Labyrinthian, in a circle room, which has a wooden mask, you put it on, and you go back in time, to where you may place the Masks to get the Secret One.
As this game has many things to do, which requires many things only obtainable ONCE. This game can get really irritating. So, have fun on your travels. Alduin's death looks very epic. You should totally try your best to get to him, just to see his death.