When you have leverage over someone you can Manipulate them to get them to do what you want.
When is making a deal with someone manipulation, and when is it just making a deal? Every transaction could be viewed as manipulating someone into giving you something in return for the money which you are using as leverage, but that's tedious and I suspect not the intent of the rules. But what about paying someone to do something they wouldn't otherwise do? That could be a bribe, using Manipulation, or it could be offering a barter with strings attached (automatically hitting a 10+ on Manipulation), or it could just be a deal, no mechanics attached.
This came up in play when a Hardholder wanted to hire the Savvyhead to work on a project, I had him roll because "to do it, do it", but now I'm questioning whether that was really manipulation or not.
There are plenty of situations where leverage is being used to get someone to do something they otherwise wouldn't, and I suspect it's not manipulation, but I can't put my finger on why not. Thoughts?

Sometimes it's easy to come up with a move when a roll fails. When a character is acting under fire it's usually clear what the danger is. When they are going aggro or seizing by force it's usually a dangerous situation, so again it's clear what could go wrong. A failed roll to open your brain is sometimes tricky at the start of a game when it isn't clear how the Maelstrom works yet, but eventually I know what the risks are.

But when someone tries to read a situation or a person, or manipulate or seduce someone, it often isn't clear to me what a failure could or should mean. I think part of the issue is that the player is making these rolls to gain knowledge or advance their goals, and not to prevent something bad from happening, so it isn't obvious what dangers there are, above and beyond simply failing.

Do you have any favorite hard moves for failed Sharp/Hot rolls that might be broadly applicable? Or do you have any suggestions for assessing what an appropriate hard move might be when nothing is jumping out at me?

Two elements of Fronts rules were non-starters for me- Fundamental Scarcity and Stakes. But I suspect I may just not be getting something, so I was curious if anyone could make a pitch for them, or tell me about your positive experiences using them. I'm hoping something will "click" for me so they can become useful elements of my prep.

I'll comment a little more about my experiences in the hopes that it will help you zero-in on what isn't working for me.

Fundamental Scarcity: On my first read through, I liked how they drew attention to scarcity as a core theme of the game, but found it odd that Hunger and Thirst were distinct, and found some of the examples strange (why are the Burn Flats associated with Ignorance?). When I first used the rules after my first session, there were threats I wanted to group together but which didn't share a common scarcity, like the cultists and the disease they were spreading- the cultists represented despair to me but the disease threatened the water and so were associated with thirst, but it seemed to me they should belong to a common front. Or the slavers, whose Warlord was ambitious, but whose lieutenant might have been a better fit to despair and whose foot soldiers are more motivated by hunger. Should I be grouping these threats into fronts by scarcity rather than the conceptual groupings that seem more natural to me? Is there an advantage to tying them into a common scarcity instead of whichever seems most natural for each?

Stakes: My problem here is that the things in the story I am the most interested in finding out are mostly about the decisions the PCs will make. What moral lines they will cross, what they are willing to do to achieve their goals, whether they can put aside pride to work with a common enemy... Those kinds of questions about NPCs aren't as interesting to me since I am usually the one who decides those, and the questions about the physical welfare of the NPCs, which the examples seemed focused on, just haven't gripped me as much. Maybe as I get better at fleshing out human NPCs I'll get more concerned with their welfare, but so far there haven't been a lot who I really cared whether they thrived or suffered.
The other problem I ran into here is I didn't find that picking out a couple stakes changed my MCing during the game. When I decided that which NPCs got sick was at stake, I couldn't really see any difference in how I MC'ed the next session versus how I would have handled it if I hadn't singled that out as an issue at stake.

Also, on a totally different note, I saw two oddities in the rules that looked like they could be typos, but I wanted to check...
1. Page 59 and 252
"your gang is a pack of fucking hyenas. Want: savagery."
Should that be "Cue: Savage"? From the chapter on stuff it looks like gangs can have the savage cue to indicate that they behave horribly, and the savagery want means that when a holding is in want that society breaks down. The cue seems appropriate here.

2. Page 58
"• an armory of scavenged and makeshift weapons.
• a gang of about 40 violent people (3-harm gang medium unruly 1-armor)."
Is that really supposed to be a 3-harm gang? My impression was that gangs get harm assigned based on the weapons they are armed with, and every other example of a gang using scavenged and makeshift weapons gets 2-harm, which makes sense to me since crowbars, knives, and handguns all do 2-harm. Or is it just a perk of the Hardholder that their gang inflicts one more harm than a similarly armed gang would for anyone else?