Prevent Excel Crashes, Optimize Formulas

I’m working with a multi-sheet workbook whose linked formulas are pushing Excel to breaking point. The file calculates an HRN value on one sheet, then looks up that result (across threshold tables) to return:

• a Risk category and an ENU rating based on where the HRN falls between two limits

The second calculation looks at the likelihood and consequence value from the master sheet to look up the risk table to get the risk rating and the inspection interval

Right now the logic is hard-wired to specific columns; whenever I insert or reorder columns the references shift, recalculation balloons and the workbook can crash completely.

I need you to refactor these four calculations so the workbook:
• stays stable and fast—even with extra columns or column moves
• uses well-structured, maintainable formulas (dynamic named ranges, structured references, LET/LAMBDA, INDEX-MATCH, XLOOKUP, whichever is best)
• contains clear data validation and friendly error handling to prevent #N/A or circular reference loops

Please start immediately; I must have a functioning, crash-free file ready for review by midday Australian Eastern Standard Time.