As Ike mentioned in a comment, you don't need to delete the whole column. You can copy the data into a temporary extra column (probably copy - then paste values). Then in the column with the incorrect column formula, you highlight the whole column (minus the table header), and choose "clear contents" (which is the crucial step - not just the delete key). This will remove the computed formula from the column (which you can test by adding an extra row). Then you can copy and paste the data back into your now cleaned column. All external formulas and other column references, will carry on working for that column without needing to recreate those references.

I know this is old thread, but I was looking for this answer, and with the help of Ike's comment, I managed to keep everything working, which was awesome for my complex spreadsheet. Wanted to add this comment for anyone following with the same issue.