Stat Changes
It seems very clear that you apply no stat changes.
This ability functions as a polymorph spell, the type of which is listed in the creature's description, but the creature does not adjust its ability scores (although it gains any other abilities of the creature it mimics).
There are no qualifiers here -- it says the creature does not adjust its ability scores, so it doesn't! The part of polymorph that you're looking at says that you
adjust its ability scores to one of these two sizes using the following table
This is exactly what the change self ability tells you to ignore.
Even though it doesn't use the word "adjustment" in the actual text of alter self, the word would generally mean any change to your stats. (And it would be a bit weird if shifting into a smaller form increased the strength of a Titan.)
Other abilities
There's nothing here to modify how polymorph spells work:
While under the effects of a polymorph spell, you lose all extraordinary and supernatural abilities that depend on your original form
Note the qualifier. You only lose the ability if it was contingent on your original form. In many places the DM will have to make a judgement call on whether that applies. But obviously, say, a manticore that shifts into human form can no longer use its Spikes special ability. The rule is intended to rule out nonsensical situations, so the change shape ability doesn't alter these rules at all.
The aasimar alternate racial trait scion of humanity can't grant access to human alternate racial traits
Up front: Don't confuse race traits with racial traits. Human (and aasimar) race traits are what the aasimar now qualifies for because of the alternate racial trait scion of humanity. On the other hand, racial traits are those specific facets of the creature's race that can be picked and traded for other facets of the creature's race because of the creature's race.
So, although the aasiamar has picked the alternate racial trait scion of humanity, the aasimar's race nonetheless remains aasiamar. Hence, an aasiamar that takes the alternate racial trait scion of humanity can no more pick human racial traits than a half-orc can pick human racial traits. An aasimar with the alternate racial trait scion of humanity could take as its two race traits Aspiring Bard and Bralani's Step, but the same aasimar couldn't take the human alternate racial traits heart of the sea and heroic.
So while the alternate racial trait scion of humanity says
Some aasimars' heavenly ancestry is extremely distant. An aasimar with this racial trait counts as an outsider (native) and a humanoid (human) for any effect related to race, including feat prerequisites and spells that affect humanoids. She can pass for human without using the Disguise skill. This racial trait replaces the Celestial language and alters the native subtype.
...this alternate racial trait doesn't give the aasimar anything the aasimar didn't already possess. Herolab shouldn't've allowed such an aasimar to pick the human alternate racial trait dual talent, first, because the aasimar's not a human, and, second, because the aasimar doesn't have the things the alternate racial trait dual talent needs to replace. That is, the alternate racial trait dual talent says that it
replaces the +2 bonus to any one ability score, the bonus feat, and the skilled traits.
And the aasimar, even if the GM allows the aasimar to take human alternate racial traits, doesn't have those other traits to trade away for this trait, making the aasimar ineligible for the new human trait, just as the aasimar would be ineligible for a feat that had as a prerequisite human and Str 70 (assuming the aasimar didn't have Str 70, obviously). Even were the aasimar to meet the human prerequisite—which it does—, it can't meet the remaining prerequisites.
Aasimar variants' ability score bonuses replace the typical aasimar ability score bonuses
That is, an aasimar gets either the typical ability score bonuses or the ability score bonuses for the variant he rolls or picks:
Players may choose one of the following six heritages for their aasimar characters in place of the traditional aasimar racial features. Each heritage presents new ability modifiers, spell-like abilities, and skill modifiers that replace the default aasimar racial traits, as well as a pair of custom traits. Each entry also discusses the most common (though by no means ubiquitous) personality traits, physical features, and places of origin of aasimars with that particular heritage.
Emphasis mine.
Best Answer
In order of your questions: Not exactly, No, and No.
1. You don't lose feats, although some of them may become unusable.
The bonus feat you received for being a human is not lost. Under the description of feats:
In Pathfinder, the polymorph effect causes a creature to take on the physical form of another creature, but it does not fully "become" that creature. A human polymorphed into a squirrel is still technically a human. I strongly suggest reading through the full description of what is changed by a Polymorph effect.
2. Polymorphing does not inherently change your race, and so racial bonuses are not necessarily lost.
The human's Bonus Feat racial trait, Skilled racial trait, and +2 racial bonus all remain, because none of them meet the criteria above. While polymorphed, you are still inherently a human, even though you don't look like one. You will temporarily lose access to your 30 foot movement speed, and replace it with the movement speed(s) of your new form.
Your character's Strength, Dexterity, and Constitution may be temporarily adjusted with Size bonuses. The rules page that I linked has a table with these adjustments, although these bonuses may depend by the source of the Polymorph effect. Usually, growing tends to cause Size bonuses to Strength and Size penalties to Dexterity, and shrinking tends to do the opposite.
For comparison, take a look at the Reincarnate spell; it actually does change a creature's race, causing them to change their racial ability score modifiers.
3. Polymorphing does not cause you to gain any feats.
The creature's bestiary page refers to a typical version of that creature; you won't acquire the squirrel's feats just by polymorphing into one.
The squirrel's racial bonus feats exist because it is inherently a squirrel. If the squirrel was polymorphed into a human form, it would have its original feats, ability scores, and skills. Due to the size increase, its Strength would get a Size bonus and its Dexterity would get a Size penalty.