As it pertains to any capital improvements made prior to me renting the home, the only way to adjust my basis is to have those costs be depreciated over the years the home was rented?
Right and you use the 3115 for that which would be filed with your return for the current tax year.....3115 lets you catch up on all of the depreciation you missed over the years.
In addition, because I sold the house on 8/17/2020 and after the tenants moved out any improvements I made to the house also cannot be added to the basis of the home?
Add those improvements to your basis.....add their cost to your adjusted basis and put that total in turbotax as your basis.
