Select a Date between Two Date Rows, then the Column State and return Table Matrix Values

I am looking for formula help in trying to write a code to pick the date from column C, in the Input Tab, and choose the row in the Freddie MAC Home Price State Index Tab that it is "closest" to it, by MONTH.

Once this date row is selected in the Freddie Mac tab, I then need the formula to next see which state (Column A in the Input Tab), the "latest" BPO Value is in (Column B in the Input Tab), and then to select that home price index value in the Fannie Mae Tab.

Finally, I need the Percentage Change in home price indexes for that state from the specific date row, specific state value to the most recent value from the bottom of the Fannie Mae tab, of course from the SAME state column of data. This will give me the percentage change in value the home price has faded or increased by, and will be placed into Column D of the Input tab. From there I can determine the "corrected" home value in column E by applying the percentage change value.

I've tried VLookUP, SumProduct, Match, Index, etc functions, clearly, I do not know how to write the code correctly.

Any help, quickly, would be most appreciated. Thank you very much.