(gamerule naturalRegeneration false)Can't you do /gamerule naturalRegeneration?
Also would be nice with teams.
/scoreboard teams add red (Add as many teams as you want)
/scoreboard teams option red color red (Set the team's color.)
/scoreboard teams join red @r[teams=,c=3] (to add 3 random players into the team, (If you want to make 2 or 4 or more players per team, change the number after =.))
/scoreboard objectives add Health health
/scoreboard objectives setdisplay list Health (to show people how much health they have (in list)
/spreadplayers 0 0 400 999 true @a (Final command you run to spread players around the 3000 block map. (1000=x -1000=z.)