1º Question:
How i can know what was a player's tools what the player was using to cancel drop or clear drop?:
Like this:

Code (Skript):

1. on drop:
2.     if player's tool is a bowl:
3.         wait 5 ticks
4.         clear dropped items

2º Question:
How i can put a number of items in variable to give a player when he join:
Like this:

Code (Skript):

1. on join:
2.     if {lc.nmr.%player%} is more or equal to 1:
3.         set slot 1 of player to {lc.nmr.%player%} trapped chest named "&c&lLoot Crate"

Error:

Code (Skript):

1. a slot can't be set to '{lc.nmr.%player%} trapped chest named "&c&lLoot Crate"' because the latter is neither an item type nor an item stack (kits.sk, line 321: set slot 1 of player to {lc.nmr.%player%} trapped chest named "&c&lLoot Crate"')