Can the +1 to Abilities that you get from Spell, Specialty, and Artifact go over the normal +6? And can Beliver Faith Healer Specialty cure Malice?
By default Abilities can't be increased over +6 from any source. You can stack lots of modifiers apart from Abilities, though. So you can have +6 Ability and -5 DR from specific bonuses and that's functionally a +11 on a roll.
For Faith Healer and Malices, I'm inclined to say yes, with the caveat that Malices generally count as life-threatening/life-changing, and so Breaking is required to treat them. Also Faith Healer may not work on all Malices---it's the GM's call as to whether things like curses and psychological issues fall under the purview of the Specialty.
I think most table would allow for Faith Healer to heal Curse and Psychological issue, since most Faith Healing in real life is about soothing the mind, and a lot of Faith Healer in the past also remove curse and misfortune. And the Archetype of Martyr healing other by taking the pain onto themselves fit really well.
How does Artifact Revalation Advancement work? Is it an automatic thing that just happen as you complete more investigation? Or do you have to actively use it in a investigation to advance it? And it is said that only the most recent Revalation applies, does this mean the bonus and penalty to your Ability and DR are also gone? What about change to Hit Point and Social Standing? Or stuff like Neglected Jeweler's Loupe power at 0 Investigation? And Can you stack multiple Artifact power together?
With artifacts, they work like this. Say you have the Battered Packet Of Spiced Cigarettes. At 0 Investigations, its Revelation is -1 DR to Stability tests. If you trade it to your buddy at the end of the investigation, you lose that benefit and they gain it instead. If your buddy carries the packet around for a whole investigation, they advance to the next Revelation (+1 Stability) but lose the benefits of the 0 Investigations Revelation (-1 DR to Stability tests.)
Basically, permanent effects like changes to Abilities and Hit Points and money stay with you even if you lose the artifact, but temporary effects like bonuses or penalties to DR or Social Standing or the Jeweler's Loupe's 0 Investigations Revelation don't.
Also you can definitely stack effects from artifacts.
The only thing you can't really do is indefinitely preserve a 0 Investigations Revelation by constantly swapping an artifact between owners. The investigator that used the artifact always advances to the next Revelation at the end of the investigation.
(This means that an investigator who carries the Battered Packet Of Spiced Cigarettes *will* get the +1 Stability Revelation, and this Stability increase will be permanent, even if they trade the cigarettes away at the end of the investigation. Also if they carry the packet around for *another* investigation, they'll get the -1 Stability Revelation, which will also be permanent, making their net Stability gain across all Revelations 0.)
Regarding whether Revelation advancement is automatic or you have to use the artifact, it's automatic. Just keeping the artifact in your home or in a vault you own will still advance its Revelations.
Optionally the GM might rule that picking an artifact up and then immediately throwing it away is safe, or that storing an artifact in some kind of spiritual containment / salt circle nullifies its current benefit and keeps it from advancing in Revelations---although the feeling with artifacts is that they're supposed to be dangerous, so I think I would probably make the players work to keep one contained.
In general, you can only take a given Specialty once. Once you've broken the Heirloom Ring, you can't get another.
For stuff like Miraculous Escape where you do Break but you automatically pass the Stability test, you can still suffer Malices. On the other hand, Languished's Rock Bottom lets you ignore all consequences from Breaking, and this includes Malices.
These are mostly up to the GM. I'd personally say yes to changing NPC Morales and recruiting monsters under certain circumstances, but different GMs may handle this differently.
With NPCs, their stats are meant to be written in a simple and quick way. You could give them a full PC style set of Abilities, but this would take more work and slow the GM down when they introduce a new NPC. The recommended thing to do is give them specific skills (e.x. Climbs Walls DR 8) when relevant, and then you can modify these further with circumstantial bonuses and penalties when appropriate. But if an NPC is really important, you could give them Abilities instead.
For Dusty Sachet Of Bitter Herbs: If you choose not to make the tea, will you die? Or is this Werewolf curse different from the normal one? Can Dismiss into Figment affect gods? Like can I Dismiss into Figment the history of King in Yellow?And Is the DR 16 on Leash The Departing Soul for the Haint to turn or not turn on you?