Chapter 2: The Gorgon Queen's Lair

Omoros's blows are accurate, but the power is weak. The snake man lives, though barely.

Kelnes moves forward and strikes at SM2. If he falls he will then move 1 square forward and attack SM4. Bonus action PAM attack as well

Completely forgot about him. For now I'll say he's in the hallway, not really able to see past everyone and not sure if it is safe to shoot anyone without hurting one of you guys. if the hallway clears up, i'll add him.
The rules state "Whether a creature is a friend or an enemy, you can’t willingly end your move in its space." I'm not 100% sure if "end your move" means when you decide you are not using any more speed for the turn or if it means anytime you pause your movement, even if you are going to move more later. How i'll rule it is that you are squeezing in order to be in an ally's space, thus you have disadvantage on your attacks as you don't have the arm movement you normally do since you are in such a small space with someone else. Lucky for you, SM2 is prone so the advantage from melee attacks against him would cancel out that disadvantage, but if this comes back up note that I will rule you are squeezing if you try to do that.

And yes, the first guy dies so you move forward as you said.

Note: I did not see anything about looking down or not at the end of your turn, so you also have to make a save when the medusa's aren't incapacitated anymore. No one has said they are, so if you have line of sight to the medusas and are within 30 feet, everyone is making a save then (Chironides already did his saves earlier).

Kelnes averts his eyes as he then casts Fog Cloud originating on T43.

Let us even the odds with these creatures!

yes, if the medusa cannot see you or you cannot see her, no need to worry about petrification. However, anyone that is in the area or who would be looking at something on the other side of it is effectively blind. Now, the rules are weird. RAW: unless someone is hiding, you can hear the sounds of things they do, like walk, and thus you know generally where they are. While you are both blinded (which is the case when botha are in heavily obscured area), everyone makes attacks without advantage or disadvantage because you have both (advantage for them not seeing you and disadvantage for you not seeing them), with Kadmos as the exception for his blind fighting style who would have advantage.

Note: unless you have blindsight like Kadmos, no one will trigger opportunity attacks. This is because even though you know they are there they are still functionally invisible so by the time you hear them walk away they are already too far away.

Isaiah moves forward still expecting worshipers to attack him, but he thro another luminous arrow while elemental keep attacking.

Chiron attempts to break grapple and return to last position and retrieve his equipment.

Isaiah kills one of the snake men (who didn't attack earlier because they weren't aware of you or that combat had even happened, so they were surprised) and Chironides moves back to the left of Kelnes, stomping around until he hears his hoof slam into his shield and picks it up.

Kadmos will advance, finding an opening and navigating his way into the battle. Once he tracks down an enemy, he attacks!