If there are roughly 140M jobs, presumably there are 140M people working those jobs, meaning that there are approximately 140M people who must cover that $6.4T, which works out to be ~$46k/yr for each working person.
If we assume we can completely wipe the following off the books: Social Security ($773M), Income Security ($541M) and Medicare ($471M), the net cost per year drops to $4.6T/yr, which works out to be ~$33k/yr for each working person.
Total federal income tax in 2013 was around $1.3T (Individual) + $273B (Corporate) = $1.59T. An increase from $1.59T to $6.2T is about a 290% net increase.
I did some very rough spreadsheet-math with  and  and came up with the following. If we didn't tax the $20k at all, and left everything the same as last year, the bottom 77% would be a net negative of ~$1.2T assuming all of their income tax went directly to pay for the $20k.
I assumed that the number of people in the top 2% made the same average salary as the top 1% in , and came up with the top 2% of income tax payers as being a net positive of $1.4T. I made that assumption just to make the math easy and to err on the side of optimism.
The 78-98 percentile come out to be a net positive of approximately $350B.
Looking back at the $1.3T federal income tax total for individuals, this would mean that after the $20k/person was paid for, the total federal income tax dollars would be roughly $600B (Individual income tax) + $273B (Corporate income tax) = $873B.
Looking at , it seems that there was a $3.803T - $2.902T = $901B deficit last year. If we knock off the difference in income tax revenues ($1.59T - $873B = $717B), then suddenly we have a $901B + $717B = $1.618T deficit again.
This all assumes that jobs stay constant, of course. I realize that all of these numbers are very rough, but I had some fun doing spreadsheet math so I figured I would share!
I'll give you just one to try and add to your spreadsheet: When you add a saftey net and provide money to those that, otherwise, would not have it to spend you obviously increase government revenue through new employment and taxation. How would you quantify that increase? I don't think anyone can say, but it would happen and it would be significant.