The Greek word oikonomia, which the KJV translates as "dispensation" can mean several things, but generally it means an ordering of things and specifically a task of ordering things assigned to someone.
Thus in the examples from 1Cor9, Eph3 and Col, Paul is discussing a "dispensation" or task given to him personally - i.e. God has tasked him with spreading the Gospel.
The example from Eph1 describes God's ordering of the world.
In none of these examples is it even suggested that God has created two or seven or any number of separate orderings of the world ("dispensations") to different ethnic peoples.
Your definition doesn't fit the verse...
1Co 9:17 For if I do this thing willingly, I have a reward: but if against my will, a dispensation a task of ordering things of the gospel is committed unto me.
However, if you don't like 'dispensation' we can use administration...
1Co 9:17 For if I do this thing willingly, I have a reward: but if against my will, a dispensation administration of the gospel is committed unto me.
Now that ,makes a little more sense than task...
But look at the context...If Paul does something willingly, he gets a reward, but if he does it against his will, it is not the grace of God working in him...And something else is comitted onto him...
You guys would be better of if you would just believe what you read...