If you read and understand his statement, I must salute you.
Every month's contributions to OA and SA are deducted to pay the housing loan. In other words, OA and SA would be zero immediately after the deduction.
The contributions to OA and SA hardly reach $40 except those months that he took a second job. Obviously, the deduction from his CPF is far short of $359 needed to pay the housing loan. Hence, the difference got to be paid out of pocket from his monthly wage of about $1k and monthly payout of $486 from Jul 2013 (now kosong).
I am puzzle how he managed to have about $3k in OA and $300 in SA in Mar 2020 when every cent in OA and SA goes to pay for housing loan ... unless some extraordinary transactions took place between 2013 and 2020.
Even if he decided at some point in time to stop using CPF to pay for the housing loan, the accumulated amount of current (Mar 2020) OA and SA should be quite close or about the same in amount as monthly contribution to OA and SA is about the same (instead OA is about 10x more than SA), except for the interest credited at end of each year.
From Jul 2013, his monthly payout of $486 from RA should remain fixed, after some changes on 1 Jul, until he exhaust his RA recently.
Now he has no more monthly payout to meet the monthly housing loan, though he can still use his OA/SA to tie him over a few months. Hence, there is a real need to help him as his wage, if he is still working at 72, is not enough to support himself and his wife and meeting the housing loan in time to come (when his OA/SA is exhausted)
If you need to top up his RA so that he can continue to receive monthly payout (to meet the monthly housing loan), better meet CPFB to find out more about the topping up and payout therefrom. Suggest that you also made him withdraw all his OA/SA and dump it together with your top-up to his RA. Whatever cannot be withdrawn from OA/SA, move it to RA.