I think this wrong, is clear in this section that both responses described in this post trigger at the same time, "After your hero attacks an enemy " and "After you use one of Nova’s basic powers", as stated on the last bullet point:

Playing Ghost Spider vs Misterio, the side scheme Analysis Paralysis is drawn from the encounter deck, its instructed to fetch the nemesis side scheme from the different areas and add threat to Analysis Paralysis equal to the threat on the nemesis side scheme, however, the nemesis side scheme was already in play (didn't search anywhere), it had at the moment 5 threat but that amount of threat was not added to the just drawn Analysis Paralysis side scheme, staying at 1 threat. I believe it should have added the 5 threats from the nemesis side scheme since that effect on Analysis Paralysis must be resolve regardless of finding or not the nemesis side scheme from other areas.

[0.5.9.53]-ghost-spider-mysterio-expert-(116)-(1678789593).json
While playing Sp/Dr, using Assess the Situation, the +1 bonus to hand size is lose after changing form, it shouldn't since "You" reference to your identity regardless of Hero or Alter-Ego form. Somehow it gets unapply, according to the log.

The Flow of trigger resolution is right here:

As point number 2 states, this all can be trigger in any order. These are all the triggers separately:
After a [character] attacks an enemy/minion---------------> This is the same as using a basic power, in this case exhauste and target an enemy
After a [character] attacks and damages an enemy/minion
After a [character] attacks and defeats an enemy/minion
After a [character] is attacked
In your code,
AfterUnitAttackUnit = AfterUnitUseBasicPower
The last source to settle is a direct quote from FFG, I'll try to get a response on the matter
I think you cannot, since removing a Stunned status cards requieres to replace an Attack, since there are no valid targets for the attack event it cannot be played (initiate an attack), since it cannot initiate an Attack, there is no effect for the Stunned status card to replace, ergo, Into the Fray cannot be played.
As you said, both text are different "After your hero attacks an enemy, …" and "After you use one of Nova’s basic powers, …", however both text refer to the same timing point, both happens at the same time, the same happen if you defend, both trigger at same time "after the hero defends" and "after a hero uses a basic power".
Sadly, this is not spell out quite bluntly in the rule book reference 1.6. The closes thing is this section:


In the rest of the book there are no mention of a response of using a "Basic Power" in any timing sequence (see last image), only references to the core use of said basic power: Recover, Attack, Thwart, and Defend. I understand that changing the current engine is something more difficult to do than fixing a card bug. Maybe this is not the highest source of confident, but asking around Discord servers, people of the community sims to agree with my assessment.
To complement on the sequencing, in the same timing point we are discussing here, abilities labeled "After a [character] is damage" and "After a [character] is defeated" happens at the same.

Regarding your Shield Toss example, I get that Janbjorn trigger after the resolution of the event since it is a single instance of an Attack, regardless of how may cards are discarded. Will Janbjorn fire 3 times after playing Dance of Deth since it is consider as 3 attack instances??
Using Janbjorn on Nova, using a basic attack should allow me to choose which ability to use first (ready the Helmet with Nova's response ability or using Janbjorn) since both triggers at the same time, after using a basic power and after and the hero attacks. That way the resource from the Novas Helmet can be used for the Janbjorn trigger.
Also, playing The Locust Ally allowed me to return any Aggression Card, it should be only Aggression Events. Here is the deck tested.
*In the next Black Panther pack there are a lot of cards that triggers after a basic power is used, it would be wise to check the timing sequence so no issues like this arise in the future.
For some reason, in this instance, Team Building Exercise reduce the cost of one event in my hand by 2 instead of 1. This only happens with this one event, other cards in my hand are reduce by 1.

The treachery Threat or Menace resolve, I was able to change to any upgraded forms (hero or alter-ego).
As stated in the title, here is the save file.
https://pastebin.com/DeGwmAwq
Here there are:
1.- Masters of Evil whiffs (nothing happens) when the only Masters of Evil minion in play is with a Wrapped in Metal attached, in this case no attacks were performed so you should search a Masters of Evil minion on the deck or discard pile.
2.- For some reason I was no able to play Wrapped in Metal when engaged with 3 minions, 1 of them had all ready Wrapped in Metal attached, 1 was not an Elite minion and the third was an Elite minion, when paying for the Wrapped in Metal in my hand the only available target was the minion with a Wrapped in Metal all ready attached to him.
3.- Mutan Mayhem event was able to return 2 x-men ally to hand, no Children of the Atom in play.
Paying for a card does not require any specific resource (fist, lighting, mental or wild), you can use any type. The exception to this are card with a requirement like Spider-Man - Peter Parker.
Also, you can use the sync ratio ability on Sp//DR Suits as many times as you like (and can) for a single card, the resource ability is not limited to 1 on any giving card played.
It's turning Iron Man into a Guardian Ally with Honorary Guardian, getting upgrades on him for -1 cost, and drawing a card with the Guardians of the Galaxy support every time you put an upgrade on him :)
Sorry for my late response.
You are absolutely right, the last card on the encounter deck was the las minion, I didn't see like that because the animation is so fast, and when the minion is discarded it put itself on top of the newly reshuffle deck make it look like it was the first card on the deck.
The deck is from a well know content creator of Marvel Champions on youtube, here is the link!
Venom - Guardian of the Galaxy Deck Factory!
Playing against Klaw using the Master of Time encounter deck, the side scheme Light Of Centuries Sphere is defeated with a few cards on the encounter deck, the encounter deck emptied so it reshuffles but continues to discard until a minion is discarded (the first card on the deck). The effect should wiff since no minion was discarded before the deck would empty.

I played Pirouette and Punch · MarvelCDB against Ghost Spider Obligation, the villain received 3 damage but the obligation went into the table without attaching George Stacy from my play area, it was ready and available to be used, is like my event canceled a non-existing when revealed effect allowing the support card to stay in play.

As the title implies, currently there is no chance to see the entire deck when you use abilities that searches through them.
One example is One Way or Another event, if there are multiple targets on the encounter deck you get to choose from those targets, if there are no targets nothing happens, this is contrary to the real life experience where you get to see what's left on the deck and is positive for strategic decisions, also you get a chance to shuffle the deck which is a positive if you play a scrying ability or somehow saw the top of the deck and want to change the outcome of the next card revealed or use in villain activation.
Other examples include Past Machinations (Kang, #43) and Forge (Storm, #22).
Thanks for your attention.