* Does the DC of the Nosoi's abilities go up as the master's levels go up? The line "Hit Dice: For the purpose of effects related to number of Hit Dice, use the master’s character level or the familiar’s normal HD total, whichever is higher." Is the answer different for spells (which aren't based on hit dice I think) and Haunting Melody (which appears to be).
Alright, so that sentence about Hit Dice has no effect on any of the familiar's abilities at all. It won't get more skill ranks or feats, and the Save of its poison or Supernatural Abilities won't change.
It only means that if the Familiar is targeted by an effect that has a different result depending on what your Hit Dice is, then you use the Master's level in place of the Familiar's Hit Dice.
For example, a normal Nosoi can be put to sleep by the Sleep spell, as it only has 3 Hit Dice. A Nosoi acting as a familiar to a 7th level Wizard would count has having 7 Hit Dice, and therefore be immune to the Sleep spell.
* How about the duration of the Haunting Melody ability? Does it scale with the master's level (is it an "effect related to the number of hit dice"?) I'd say this is a clear yes, but Hero Lab seems to go with no.
As explained above, Hero Lab is correct.
* Can starting feats be replaced in a familiar? It seems like _some_ feats can replace starting feats, but heck if I can find anything on that. Weapon finesse is useless on a tiny familiar.
Yes, starting feats can be replaced.
Reddit Thread with the 4 feats linked
As said in the thread, if it's not for a Society game you could theoretically take any feat the Familiar qualifies for. Additional Traits is a good option for home games, as it allows you to pick up class skills and strong supportive traits such as Helpful and Agent of Chance.
*What do you do if there aren't enough class skills listed? The Nosoi seems to be missing ones. UMD or (for RP reasons), heal, might be really nice...
With the exception of the Karmic Blessing spell and Additional Traits, I know of no way to get Class skills. But remember that class skill is just a +3 bonus. If you, the master, have 4 ranks in Heal then the Nosoi would have a Heal skill bonus of +5. Allowing it to Provide Long-term care with a Take 10 on its check.
But there's always Familiar Archetypes. The Emissary archetype grants your Familiar the Heal, Knowledge (Religion) and Sense Motive as class skills. Remember that Improved Familiars lack the 'Speak with Animals of its kind ability', so there are few Familiar Archetypes that Improved Familiars can take.
* Does the DC of the Nosoi's abilities go up as the master's levels go up? The line "Hit Dice: For the purpose of effects related to number of Hit Dice, use the master’s character level or the familiar’s normal HD total, whichever is higher." Is the answer different for spells (which aren't based on hit dice I think) and Haunting Melody (which appears to be).
The silvanshee familiar was errata'd, that means they didn't want that portion to level with familiar HD. That means the default is that DCs do scale with the master's HD if they are HD based.
See This Post and nearby ones for further details.* How about the duration of the Haunting Melody ability? Does it scale with the master's level (is it an "effect related to the number of hit dice"?) I'd say this is a clear yes, but Hero Lab seems to go with no.
Not only does the DC scale, so does the max rounds because the HD is greater.
* Can starting feats be replaced in a familiar? It seems like _some_ feats can replace starting feats, but heck if I can find anything on that. Weapon finesse is useless on a tiny familiar.
I don't know about this.
*What do you do if there aren't enough class skills listed? The Nosoi seems to be missing ones. UMD or (for RP reasons), heal, might be really nice...
A Nosoi is an Outsider. Their skills are defined as: Bluff, Craft, Knowledge (planes), Perception, Sense Motive, and Stealth.
Outsiders also receive 4 additional class skills determined by the creature’s theme.The Bestiary entry for a Nosoi lists: Fly +17, Knowledge (history) +6, Knowledge (planes) +6, Perception +9, Profession (scribe) +7, Sense Motive +3, and Stealth +17
[General monster rule: ranks only go into class skills, and max ranks to any skill invested.]
Removing outsider skills, that leaves: Fly, Knowledge (history), and Profession (scribe)
Therefore, a Nosoi's class skills are: Bluff, Craft, Fly, Knowledge (history), Knowledge (planes), Perception, Profession (scribe), Sense Motive, Stealth, and one unnamed skill with no ranks.
Talk to the GM about the mystery skill. Maybe you can negotiate something nice.
As a familiar, it gets to use your ranks in its skills, and if you have a rank in one of its class skills, it will get the +3 for that skill.
I had a familiar use my ranks in UMD to use a wand of CLW on me when I was negative.
/cevah