http://blog.wenxuecity.com/myblog/72332/201709/23374.html
Current income $300k
Retirement expense = $300k x 0.75 = $225k
SS income @66 = $36k x 2 = $72k
Income generated from asset = $225k - $72k = $153k
Asset needed to generate $153k = $3.825M x 0.04 = $153k
You are not too far, just double your asset. You will be there.