it's reported that most of the familie‘s income is 3 times o

这里的what引导的从句是跟在3 times后面的,"or more"是个补充说明,所以不是比较状语从句,不能用than,
3 times what it was three years ago“是3年前的3倍”.倍数的表达方式：times + 名词+ of,比如：His room is twice the size of mine.他的房间有我的2倍大,= his room is twice as big as mine.
例句中what 引导名词性从句,代替的就是上面我说的times后面跟的名词.

据报导大多数家庭的收入是三年前的三倍或者更多，what指的就是收入的多少

it was 后面缺什么，缺“什么”吧，那就用what 呗