Hey there, thanks for trying out the game. In terms of answering your questions.
- I use the "Firearms" skill for grenade attacks.
- Only the stun grenade requires and additional save and I believe this is stated as the Fortitude skill and would apply to anyone in range. Anyone in range should use the attack roll result as the target score for saving (this may not have been explicitly stated I would have to check over the rules).
- Actions are currently "move or act" on a rules as written basis. I was emulating the X-Com tactical style of combat and envisaging this to be a minis type game but feel free to adopt a "move and act" approach.
- Armour is intended to act as additional health points and depleted first before health so it effectively gets damaged and becomes useless after a few hits which increases the risk to the players. The intention was this game was quite deadly (almost like a funnel type game approach) but feel free to play around the with stats and approach to suit you.
Once again, thanks for the feedback. It's great to see that you have 'house ruled' the game to suit your own preferences.