As far as the money for Snidge goes, I think this made perfect sense. After all Berg is a raging Barbarian who is a slave (even if at the moment he is 'free'); he's not the type that would know about building costs or anything of that nature. Likewise Azriel is an angel descended from the heavens. He was in the mortal world purely to help Raziel, so it's unlikely he's spent a lot of time learning about mortal architecture and building practices.
That, and realistically the amount of gold they had wouldn't actually accomplish all that much if he tried to be that realistic. For example, in the DMG to build a simple outpost or fort is 15k gp, and a simple trading post is 5k gp. So even if they'd given all the money to Snidge, by the rules of the DMG (and they are trying to stay relatively by the rules in CoS) the money was chump change. So by keeping it vague and open ended, Adam has the freedom to do more with less.
As for the gang situation, we seem to have understood it differently. From what I remember (and it is the next day, so maybe I'm remembering it wrong) but the thugs that showed up didn't know the house was sold and weren't the brains of the outfit. They were sent to get the money, demanded it, and when they realised they were in over their heads, they left, saying they'd bother the Blacksmith's family instead. So as far as I'm aware the party isn't expected to pay her debt. They're mainly involved in this issue now because they want their armour, and the thugs fucking with the blacksmiths puts their investment at risk.
As for why the gang corruption thing is going on, that's just Adam making his world breathing and real. He could have just hand waved a week of their lives and said 'Yeah, you wait for your armour and then it's done; now what?' but instead he's letting them live out that time and in doing so making the npc's and the city matter. They now know more about who these smiths are, how worshipper's of The Lover's behave, and it also tested the morals of the party. I certainly didn't know if any of them would just try to murder the thugs, or if they'd try to talk their way out of it. I didn't know if they'd try to protect the smith's, raid the thug's base, or simply gamble and hope for the best.
That's part of what I love about Adam's style. The world grows and lives beyond the scope of the party, and not everything they see or encounter has to have some grand quest hidden inside of it. Sometimes it's just the lives of the pc's and some npc's crossing paths, and it's entirely up to them whether or not they get invested in that or not.
So to answer your question I don't think Adam really has a plan for this gang situation. He'll end up making one now I'm sure, but I assume it came up because the party asked for immediate housing with no questions asked, and someone trying to escape debt collectors certainly would fit that bill.