Thank you for very interesting question!
here are some results
The first part is accumulated phase - you only add to saving and spend from other sources. The second phase - there will nt be any additional to saving - only interest and spending.
Spending is inflation adjusted (based on 5% inflation).
Additional also inflation adjusted - you would need to save $49,925 annualy in this year and it will be $77,450 in ten years from now.
You will have ~$1,100,000 at the time of retirement. The maximum saving will be $1,222,519 in 19 years and will start to go down because of spending increase (inflation adjusted). So far by the time your father plan to die his estate will be $54.
Please find HERE the excel file I created - so you may compare with yours.
PMT(rate,nper,pv,fv,type) - is the financial function that used also in Excel - it calculates the payment for a loan based on constant payments and a constant interest rate.
However, in your situation - payments are not constant - but inflation adjusted. Is it possible that spending will not be inflation adjusted after he retired?
providing that spending will not be inflation-adjusted after retirement - and payments will not be inflation-adjusted - that amount will be $33,109.