According to the wiki (and confirmed by personal experience) certain zombies have the ability to pick up and wear a set of armor and wield a single item in their hand. See Armed Zombie
Therefore, if you are looking for your stuff, a set of your armor (what you were wearing or carrying) may be on the zombie still, and an item may be in its hand, but the rest of your stuff should be on the ground unless it has despawned, which I believe happens after 5 minutes of being in a loaded chunk.
Yes, there is a way in the 1.8 snapshots.
Using a RedStone clock give all entities that damage the player a huge weakness effect:
/effect @e[mob id] 18 9999 127
Note that @e targets players and thus so that only mobs get a weakness effect you have to put in an ID for the entity type. You will have to have a few command blocks each for each type of hostile entity(One each for zombies, skeletons, endermen, creepers{change gamerule doMobGriefing to false}, zombie pigmen, ghasts and blazes). This prevents them from doing damage to the player. Note also that if you give them a weakness level of more than 127, it has a negative effect, meaning it will give them basically 127 strength.
Another method that can be used in 1.7.x is giving all the players a resistance effect like you did but weaker, and then giving players a strength effect that overpowers the resistance.
Strength:
/effect @a 5 9999 6
Resistance:
/effect @a 11 9999 4
This will give all players resistance 4 and this is enough to make them invincible to mobs. They will still take hits but will not take any damage. Note: I am not actually sure if Strength 6 is enough to overpower Resistance 4. If it isn't, just give a higher strength. If the Resistance is too low, give them a higher resistance and higher strength. Just look for the balance. :)
A few questions:
- Is there a reason you are not making it on Peaceful mode? (I imagine it is so that players don't regenerate health that quickly but you can turn the gamerule naturalRegeneration off)
- Is there a reason, if you don't want to turn it to peaceful, why you want to keep gamerule doMobSpawning on?
- Are you manually spawning the mobs, i.e. with command blocks? If yes you can modify their attributes to not allow them to damage the player.
So yes, there are ways to do it in vanilla Minecraft.
Hope I helped!
Best Answer
Create a team:
Join the team:
On a clock, make all zombies join the team:
Mobs in the same team as you will not attack you.