Expert..What should we do if we did a mess of MIGO and MIRO in PO history?

Question

Much appreciate if anyone could help on this issue.
What we have done:
we have a Purchase Order of 3 line items with the quantity in 300,200,100, respectively. the net price for each unit is $1.
In MIGO:
1. we posted MIGO with wrong quantity and wrong 'amount in LC' as follows:
quantity = 1;
'amount in LC' = $ 600
2. we reverse this goods receipt with correct quantity and wrong 'amount in LC'.
quantity = -1;
'amount in LC' = $ -1
In MIRO
we wrongly posted the receipt as follows:
Quantity = 350;
Amount = $ 350
then again, we did another wrong thing:
we deleted the line items 2 and 3 in Purchase order in order to close the commitment in the Project.
Now we are end up to a very bad situation:
The invoice amount is not matched up to the PO, and
the Project still can not be closed due to the commitment sitting in the Project WBS.
What should we do now, experts???
Much appreciate if you can help us out.
Points are generously assigned!

Answer 1

To Kishore Kumar Chiluka,
I finished the first step - delete line item 2 and 3 successfully.
Now I start to reverse Goods Receipts posted against in 1st line item.
In the PO history of 1st line item, we posted the following material documents.
1. wrongly post MIGO as follows.
Movement Type = 101
quantity = 400;
'amount in LC' = $ 400
2. tried to reverse the wrong material document as follows, unfortunately, 'amount in LC' again is wrong.
Movement Type = 122
quantity = - 400;
'amount in LC' = $ - 500
3. Now we want to follow your instructions to reverse step 2 using MBST, however we end up with the error message saying
PU Ordered quantity exceeded by 400 EA. Message no. M7022.
Diagnosis
The specified stock level or quantity is exceeded by 400 EA.
What should we do to cancel the wrongly reversal material doc in step2??
in addition, we do not have idea how 'amount in LC' again is determined, because we did not put in ount in LC' = $ - 500.
Much appreciate for your help!!
Points are generiously given.