Adding extra armor points with attributes

UUIDLeast and UUIDMost are used to create an ID number that is different from the rest to label each attribute. They are not a range of numbers. If set them all to 1 and 1000 and it will not pick a random number in that range. Think of them as pairs. The pairs have to be different for each attribute. If you use the same pair to label different attributes, you are actually creating a conflict which forces one attribute to overwrite another.

In your example you have 4 items, each with 2 attribute modifiers. This means you need 8 unique pairs of numbers.

One possible solution would be UUIDLeast:1 and UUIDMost:1-8.

That would look like:

/give @p minecraft:leather_boots 1 0 {AttributeModifiers:[{AttributeName:"generic.knockbackResistance",Name:"generic.knockbackResistance",Amount:.05,Operation:0,UUIDLeast:1,UUIDMost:1,Slot:"feet"},{AttributeName:"generic.armor",Name:"generic.armor",Amount:1,Operation:0,UUIDLeast:1,UUIDMost:2,Slot:"feet"}],display:{Name:"Stone Boots",Lore:["5% Knockback Resistance"],color:10066329}}

/give @p minecraft:leather_leggings 1 0 {AttributeModifiers:[{AttributeName:"generic.knockbackResistance",Name:"generic.knockbackResistance",Amount:.05,Operation:0,UUIDLeast:1,UUIDMost:3,Slot:"legs"},{AttributeName:"generic.armor",Name:"generic.armor",Amount:3,Operation:0,UUIDLeast:1,UUIDMost:4,Slot:"legs"}],display:{Name:"Stone Leggings",Lore:["5% Knockback Resistance"],color:10066329}}

/give @p minecraft:leather_chestplate 1 0 {AttributeModifiers:[{AttributeName:"generic.knockbackResistance",Name:"generic.knockbackResistance",Amount:.05,Operation:0,UUIDLeast:1,UUIDMost:5,Slot:"chest"},{AttributeName:"generic.armor",Name:"generic.armor",Amount:4,Operation:0,UUIDLeast:1,UUIDMost:6,Slot:"chest"}],display:{Name:"Stone Chestplate",Lore:["5% Knockback Resistance"],color:10066329}}

/give @p minecraft:leather_helmet 1 0 {AttributeModifiers:[{AttributeName:"generic.knockbackResistance",Name:"generic.knockbackResistance",Amount:.05,Operation:0,UUIDLeast:1,UUIDMost:7,Slot:"head"},{AttributeName:"generic.armor",Name:"generic.armor",Amount:2,Operation:0,UUIDLeast:1,UUIDMost:8,Slot:"head"}],display:{Name:"Stone Helmet",Lore:["5% Knockback Resistance"],color:10066329}}