For a medical expense tax deduction, you only include the EXTRA cost that was due to the medical need. If audited, you need a reasonable way of proving this--the IRS does not have to award any deduction that the taxpayer can't prove. If you don't have an itemized statement of costs, maybe you can get one from the contractor if you explain why you need it.
For the rest, you can include the total cost you paid for the pool, landscaping, and other improvements to your real property in your cost basis when and if you sell (minus the costs you deduct as a medical expense). You should keep paperwork relating to home improvements for as long as you own the home, plus 6 years after, since improvements made long ago can affect your tax returns in the year you sell.
