So I decided to get people to join me in a test run for zombiies in a new map, and note that I used the command in FREEBUILD. so the command is /infection, it worked okay for a few hours of use, then this bug came up that everytime a zombie infects someone, everyone gets infected and the game ends, this doesnt leave after a server restart. If you want to see it for yourself please check up on my server on LeeIzaZombie Freebuild and Game (please note that it is not 24/7)
And for /cmdblock happiness 2, It works pretty good, but there is just on minor problem that the blocks "air,lava and water" dont do the specified command when the player walks into the block.