Senate Resolution Calling for a Constitutional Convention.

[True Federalist (진정한 연방 주의자)]

Since you're going for proportional, here are the priority values for each Region with the current registered population.

(1) NE 49 voters
(2) ME 23 voters
(3) P  22 voters
(4) SE 22 voters
(5) MW 15 voters
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(6) NE delegate #2 PV 34.65
(7) NE delegate #3 PV 20.00
( ME delegate #2 PV 16.26
(9) P  delegate #2 PV 15.56
(10) SE delegate #2 PV 15.56
(11) NE delegate #4 PV 14.14
(12) NE delegate #5 PV 10.96
(13) MW delegate #2 PV 10.61
(14) ME delegate #3 PV 9.39
(15) P delegate #3 PV 8.98
(16) SE delegate #3 PV 8.98
(17) NE delegate #6 PV 8.95
(18) NE delegate #7 PV 7.56

6 delgates, 11 delegates, and 17 delegates make good breakpoints.

[True Federalist (진정한 연방 주의자)]

Yes.

[True Federalist (진정한 연방 주의자)]

This system is the same as that used to apportion the US House, which is called the method of equal proportions.

Step 1: Give each State a seat (Region a delegate).

Step 2: Determine for each State its priority value.
The priority value is equal to the population of the State divided by the square root of n*(n+1) where n is the number of seats it current has.  At the start this will be dividing all populations by the square root of 2 (2=1*2)  to get the priority values, then by the square root of 6 (6=2*3), square root of 12 (12=3*4) etc. as States add seats.

Step 3: Give the State with the largest priority value a seat and recalculate its priority value based on the fact that it has an extra seat.

Step 4: Until you have the number of seats you want,  repeat Step 3.

(Or alternatively, you could decide a priori that the cutoff will be at a certain priority value, if you don't want a fixed size for the group.

[True Federalist (진정한 연방 주의자)]

It also specifies that the President is to call for the Convention.

[True Federalist (진정한 연방 주의자)]

Well, I picked an alternate, because I hadn't had the chance to confirm all of my choices by the time I made the announcement.