You keep assuming all $$$ are spent immediately in your deficit estimates. Likely not true, especially for the reasons you state and others. Also, the government fiscal year ends 9/30 so we're halfway through already.
It is still obscene spending as we assess a "wartime" footing for economic recovery. Of course, anyone who originally thought a real estate developer was going to be averse to borrowing money fooled themselves long ago.
I keep assuming all $$$ are spent immediately, because I'm assuming the vast vast majority of the $2.3T will be spent by the end of September. Otherwise, what would be the point? The portion that's the money back to workers and the unemployment is the largest block - that's all going out in the next 3 months. The remaining part is loans and bailouts to companies. True, people may not use the loans, but I imagine the large company bailouts will take the money immediately. But that is indeed my speculation.
$250B - unemployment.
$300B - one time checks.
$500B - large company bailouts like post office, airlines, etc.
$150B - money straight to states.
$200B - to hospitals and what-not.
$50B - safety net increases.
That's well over $1T that should be spent completely in the next 3 months. We were running a $1T deficit. That makes about $2.5T right there, if you assume about $800B (one-third) of the package doesn't get spent by end of September.
The next piece of the puzzle is tax revenue. That's hard for me to guess. But if unemployment averages over 20% for the last 6 months of the fiscal year (The Fed forecasts a peak of 32%), thats a tax revenue reduction of 20% over those 6 months roughly. That's a $200B shortfall. Payroll taxes will also be reduced largely commensurate with that, which would be another $150B shortfall. If corporate taxes fell 6% in the great recession, I think a 15%-20% reduction (based off unemployment forecasts and what-not) in profits is a good guess. Across the last 6 months of the year would equate to another $30B shortfall. That's a total tax revenue shortfall in the final 6 months of about $400B.
If you add all that up, that's very roughly $3T. I'm guessing $4T, because the House is already working on another package, Trump just proposed a different one, and I think the plummet in tax revenue will be more pronounced than what I just listed. The Great Recession was a much more mild time than what we're experiencing, and total tax revenue to the government missed the original forecasts by $1T in 2009.