Having problems spreading expense over months with partial month calculation

Question

I am writing a nested if statement that will calculate monthly expense based on an "Expense Frequency" option. Most of them see to be working but I have two that will not work for some reason.

The first problem is the "Fixed" option - I want this to put the whole expense rate in the first month of the expense period. For some reason it is not triggering in the first month. I feel like this might be a simple fix?

The second problem is a little more complex. It is the "Spread Amount" option. When the months are full calendar months the calculation is easy, divide total expense amount by # of months. But when I factor in partial months the calculation diverges from what I am looking for. The shorter the time duration, the larger the variance is from the total expense. When I stretch the expense over a longer period the variance shrinks. It is a pretty complex calculation (I think) and basically I want to use days out of the month for the calculation in the partial months (first and/or last) and then whole months in the middle. I have attempted this in my attached spreadsheet and I thought it might work but it isn't. Is anyone able to help me out here? I would even be satisfied with a succinct explanation of why this calculation isn't possible / doesn't make sense / cannot be done so I can explain this to my boss. I am providing a cash reward for this if it can be handled in the next three hours. Please help!! Thank you!

This is my formula

=IF($I9="Spread Amount",IF(AND($J9<=O$6,$K9>=O$5),IF(EOMONTH($J9,0)=O$6,(($M9)/(DATEDIF($J9,$K9,"m")+1)((O$6-$J9+1)/O$4)),IF(EOMONTH($K9,0)=O$6,IF(EOMONTH($K9,0)=O$6,(($M9)/(DATEDIF($J9,$K9,"m")+1)(($K9-O$5+1)/O$4))),($M9-IF(ISERROR(HLOOKUP($K9,$6:9,$XFD9,0)),HLOOKUP(EOMONTH($K9,0),$6:9,$XFD9,0),0)-IF(ISERROR(HLOOKUP($J9,$6:9,$XFD9,0)),HLOOKUP(EOMONTH($J9,0),$6:9,$XFD9,0),0))/(DATEDIF($J9,$K9,"m")))),0),IF(O$7>$K9,0,IF($I9="EOQ",IF(OR(MONTH(O$7)=3,MONTH(O$7)=6,MONTH(O$7)=9,MONTH(O$7)=12),$M9,0),IF($I9="Spread Evenly",IF(AND($J9<=O$6,$K9>=O$5),IF(EOMONTH($J9,0)=O$6,$M9*((O$6-$J9+1)/O$4),IF(EOMONTH($K9,0)=O$6,$M9*(($K9-O$5+1)/O$4),$M9)),IF($I9="Fixed",IF(AND($J9>=O$5,$J9<=O$6),$M9,0),IF($I9="Repeat Annually",IF(MONTH($J9)=MONTH(O$6),$M9,0),0))),IF($I9="Odd Month",IF(ISODD(MONTH(O$6)),$M9,0),IF($I9="Daily",IF(AND($J9<=O$6,$K9>=O$5),IF(EOMONTH($J9,0)=O$6,($M9/($K9-$J9+1))(O$6-$J9+1),IF(EOMONTH($K9,0)=O$6,($M9/($K9-$J9+1))($K9-O$5+1),($M9/($K9-$J9+1))*O$4)),0))))))*1)

This is what the spreadsheet looks like