How much money should everyone get?

The right answer to this is not a number, but rather a feedback loop that converges on the right number. When everyone is laid off without production of goods slowing down, the result is deflation; when everyone gets too much money relative to production of goods, the result is inflation. So that means you can use the CPI inflation as a feedback variable, and adjust the UBI amount until the CPI is stable.

If the plan was to give people the full set of housing/clothing/food then use the poverty line calculation for amount of money. Or the social security calculation.

We can iterate on the exact amount. There are difficulties with UBI but figuring out the amount is a pretty minor one.