Thank everyone for all the relative insight!

I believe I found a solution with regards to amortizing mulitple loans at once; In the section where you are creating cluster indexes:

CREATE CLUSTERED INDEX IX_#amort_period

ON #amort(period)

I add the following loop:

DECLARE @loan_id INT

SET @loan_id = 1

WHILE @loan_id <= (select max(Loan_ID) from loans)

BEGIN

And it seems to be working like a charm and to the penny in my case. Thanks again for all your help! 🙂