Min and max atk/matk is basically the range of damage you can do prior to the calculation applied from skills. Example if you have a weapon that gives 27,000 - 40,000 Patk. If you attack with a skill that does 100% of your Patk, It will range from 27,000 - 40,000 damage. Skill apply % differently.
Min/Max atk/matk soulcraft on weapons affect your base attack on your weapon. Example: You have 500 Patk, your weapon gives 500-1000 base Patk. If you roll a Max 10% Patk, you will have 500-1100 Patk given from your weapon, which would most likely be 1600 Patk.
Patk/Matk +xxx affects your base max attack. Example: You have 1000 Patk total on your character, your belt of perseverance gives you +500 Patk, you will have 1500 Patk in total.
Casting speed affects your skills that require casting time. Skill animation without cast time will not get faster with casting speed. There are 2 types of casting speed, one with % and one with a flat amount. Flat amount is easy to calculate, % on the other hand is a small boost. Example: 2 second cast time - 0.5 cast time = 1.5 seconds. 2 second cast time - (5% x 2 seconds) = 1.9 seconds.
I wrote this really messy so I hope you understand or someone cleans it up or something