Going by memory (at work at the moment!)
1 -
If the investigator uses an ELDER SIGN on a STUNNED MONSTER - does the monster move?
Stunned - "Monster cannot move"
Elder Sign - "moves all monsters in the investigators Room/space - 2 spaces away from investigator"
2 -
When a combat card "moves a monster", does it move a STUNNED monster?
3 - What is the limit of TRAUMA and MYTHOS cards the keeper can have?
Is this #x TRAUMA nd #x MYTHOS? or "X number of cards in hand?"
For question 3 at least, your max hand size is 8. 4 mythos, 4 trauma. Can't do 3/5 or other combos to get to 8, 4 max each.
Just to add to the stunned debacle, do you have to evade a stunned monster? My guess is yes, but if it can't move or attack, surely you could just walk away from the beastie.
I forget Corey's exact phrasing, but if a monster is stunned at the beginning of your turn, you do not have to evade it. If you stun a monster with an attack action to start your turn, you still have to evade it on your turn.
how I handled stunned evades -
page 15 - Monsters: A stunned monster may not move or attack.
I applied this to evade checks. since it can't attack.
1. After rereading Evade Tests and the Stun Status Effect I feel stunned monsters cannot attack and there for you wouldn't need to make an evade test. However the Elder Sign is an artifact so I probably would allow it to still have it's effect. A stunned creature could not chose to move or attack (hence no evade check) but if magically repelled by a powerful artifact it could probably stagger away from it. But on the grounds I also will reserve the right to compel players to move even if stunned with uncontrollable urges. This maybe wrong but that's how I'm going to go with it until I find a better way.
2. I would also allow combat cards to move a monster (I'm assuming they are being knocked back from a player attack as they cannot attack while stunned) so yes, the blow would still move the monster back, I know it's not necessarily to the letter of the rules but it has a more realistic feel to it.
3. As everyone already said 4 mythos and 4 trauma, this can be found on page 11 of the rules of play left hand column under the heading "drawing mythos and trauma cards"
In essence, I think a Stunned monster may not move during the Keeper's turn, but may be moved by effects that move it during the Investigators turns.