Multiple Realm issues, disappearing villagers, achievements not being counted

I have spent countless hours buikding a village and finding zombie villagers to fill it, only to log on numerous times to find that my villager numbers keep dwindling. I hqve went through the village finding any and everything that could potentially hurt them to no avail. I also notice while going through and trying to complete achievements they are not being counted notable ones are creati g the iron golem, and planting flowers in pots.