Hi Malkur, from what I know, Denval had been discovered by sea, and so entrance to the City would be through a port, otherwise you're scaling mountains. Try to send a message to Tabarnac, he's the DS of Denval, and would be better able to assist you. (I'll try to point this thread his way as well)
As for your travel woes, there are many ways to beat around the bush, one is to buy enough supplies for your journey (hence no stop overs, problem solved). Based on experience, assuming that a certain unopened place will accept travelers or could be a stop over for a journey is wrong... I have recently gotten a nudge from storyteller because I mentioned that we were heading towards an unopened city in my travels for a stopover (I just got away with it by saying I'm staying on the road).
My best bet,
based from this map, from Ravok to Avanthal alone you need about two seasons of traveling and make sure it isn't winter. So maybe a Ravok-Avanthal-Denval route instead?
I just got word from Tabarnac that:
Tabarnac (whispers): He could travel by land to the Spires, but then he'd have to take a ship to Denval because it's hedged in by "impassable" rockfalls and debris.
So yeah, maybe choose to go to Avanthal and ride a ship to Denval.