Minecraft – How to you give a player fireworks

To have infinite amount of an item in a dispenser set the count for that item to -1:

/summon FallingSand ~3 ~1 ~ {TileID:23, Time:1, TileEntityData:{Items:[{id:35, Slot:0, Count:-1}]}}

To have a data value for an item in the dispenser, for example coloured wool, use the Data: tag:

/summon FallingSand ~3 ~1 ~ {TileID:23, Time:1, TileEntityData:{Items:[{id:35, Slot:0, Count:-1,Data:0}]}}

Data:0 will make it spawn white wool.

You may also want to switch to the /setblock command. Here is the same with /setblock:

/setblock ~3 ~1 ~0 23 keep {Items:[{id:35, Slot:0, Count:-1,Data:0}]}

As you can see it is much smaller. You can also use the new minecraft:<blockname> format:

/setblock ~3 ~1 ~0 minecraft:dispenser keep {Items:[{id:35, Slot:0, Count:-1,Data:0}]}

If there is already a block there then you might want to change to break:

/setblock ~3 ~1 ~0 minecraft:dispenser break {Items:[{id:35, Slot:0, Count:-1,Data:0}]} 

I also think that it might eventually run out, so you can fill all the slots with the item, unless you are going to have other items in there as well. This should last a long time though so you should be fine. :D

Hope I helped!

Your first command is fine if you are changing it as you say.

The problem appears to be that you have a space between the selector (@a) and the selector arguments ([score_Deaths_min=1]), when there shouldn't be one. Try this command instead:

/give @a[score_Deaths_min=1] iron_sword