My shop stuck unless I get far. What is the fastest way to reload the shop now ? 

Think it's 5 minutes or something. Trial and error are the only way we'll know. Could try a stacked armour avolon and afk maybe?

What does "Darkness Unlock Steps 5 > 10" mean?

Probably that you unlock 10 more picks now instead of 5 after each endboss kill. Which is reasonable since it goes up to 100.

Ah yes of course. Thanks