Your father is not in a bad position, if his expenses really are $1,800 a month, including debt repayment, and that debt is at a fixed interest rate. He has $400,000, from which he needs to draw $1,000 a month, plus enough to pay income tax on the withdrawals. At a 4 percent withdrawal rate, he could apply the safe withdrawal rate of 4 percent, and likely be just fine. That's $16,000 a year, or $1,333. Many states do not tax Social Security income, and his taxes should be fairly low anyway at that income level. Once he decides to take his own Social Security, his cash flow should improve and the withdrawals from the 401 (k) will drop.
However, at his age, he should be on Medicare. He will need to pay the Medicare Part B premium, plus Medigap insurance. I'm concerned that the $1,800 does not include the health insurance and the debt repayment. You might benefit from doing a case study on his income and expenses.
You need to pay off your credit card debt ASAP. With over $5,000 a month left over after your new expenses, that check should be written ASAP. You would probably benefit from doing a case study as well.