Main quest and levelling. Am I at the expected level?

Solution 1:

That's not really how Skyrim works, you can really be any level. There are no expectations like that, the game scales with your level.

Solution 2:

http://elderscrolls.wikia.com/wiki/Dragonslayer

At the notes it says this,

Some higher-level characters may find it less than a challenge to kill Alduin, even on master difficulty. This can lead to the whole confrontation feeling a little anti-climactic. As such, it is suggested that players be sure to enter Sovngarde no later than level 35 if they value the story (Suggested level in the Official Guide is 24).

And that's for the last part of the main quest-line.

I'm level 15 now and am halfway through the Elder knowledge quest. This was all very do-able.

I don't think that the game scales with your level answer is correct since for example i can't get passed the kill the silverhand leader quest, and i tried like 10 times, but i keep getting insta killed by a guy. I've also read somewhere that for some quests to become available there's a level requirement.