How does the Will save to disbelieve the illusion from the Major Image spell work?

Question

I'd like to clarify some things in regards to Will Save on Major Image spell. I will be quoting rules from Silent Image, because that's where actual rules are stated. Major Image is just Silent Image with bonus senses.

DISCLAIMER: I'm interested exclusively in RAW answers.

So here's list of things I'm unsure about:

1. Spell says "Will disbelief (if interacted with)". Does this mean enemies do not have a Will Save unless they waste a turn to interact with the illusion?

   Example for this: I create an illusion of labyrinth of walls made out of razor-sharp moving blades. Since most opponents won't be interested in being cut to pieces they won't ever be able to see through illusion (because they refuse to interact with it) and thus I can beeline them however I want? Correct?

2. Spell says "Will disbelief (if interacted with)". Spell doesn't say "Will disbelief (if someone else is seen interacting with it)"? Does this mean even if a single opponent sees through illusion by chance (bumps into the wall and goes through it) others don't get to see through it themselves and test their Will Save?

   Keeping the previous example, as a caster I can narrate one enemy going through the wall as being shredded to pieces, thus discouraging others from attempting it themselves. And unless they make their Will Save (which they don't get to do unless they interact with illusion themselves) they have to believe what they see. Correct?

Also: is there any rule that specifies when enemies should be "testing" the illusion? I mean, if GM just does "everyone spends his turn to test the illusion" the whole spell becomes a 1-turn Slow, which is beyond useless. And it's also heavy cheat, because enemies don't know it's an illusion to be tested, GM does.

I would rather expect everyone to go with the flow unless something seems extremely out of place. And even then, magic is common, living bladed walls do exist (I keep the same example so it's easier to follow).

3. Last but not least. This is basically a holographic movie kind of situation. As a caster I narrate the illusion in real time, I can react to what enemies are doing and narrate out anything that could lead them to believe it is an illusion. Correct?

[EDITED slightly to clarify any confusion.]

Answer 1

1. Correct

Ultimate Intrigue included this bit of guidance on illusion spells:

But what does it mean to interact with an illusion? It can’t just mean looking at the illusion, as otherwise there would be no need to make the distinction, but drawing the line can be a bit tricky. Fortunately, the rules can help to define that difference. A creature that spends a move action to carefully study an illusion receives a Will saving throw to disbelieve that illusion, so that is a good benchmark from which to work.

Using that as a basis, interacting generally means spending a move action, standard action, or greater on a character’s part. For example, if there were a major image of an ogre, a character who tried to attack the ogre would receive a saving throw to disbelieve, as would a character who spent 1 minute attempting a Diplomacy check on the ogre. A character who just traded witty banter with the ogre as a free action would not, nor would a character who simply cast spells on herself or her allies and never directly confronted the illusory ogre. For a glamer, interacting generally works the same as for a figment, except that the interaction must be limited to something the glamer affects. For instance, grabbing a creature’s ear would be an interaction for a human using disguise self to appear as an elf, but not for someone using a glamer to change his hair color. Similarly, visually studying someone would not grant a save against a glamer that purely changed her voice.

So if a party just looks at the walls and never attempts to interact with them (i.e. tosses a pebble into the blades, tries to use perception or disable device to figure out how to turn them off, etc.) they would not receive a save.

2. No

The rules for the illusion school state:

A character faced with proof that an illusion isn’t real needs no saving throw. If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.

A character walking through a solid wall of blades and shouting that it's not real, making noise as they continue to move, or walking back through would constitute proof that it's not real and the other characters would no longer need to make a save to see through the illusion.