Do they account for the covid deaths during the pandemic? Since a lot of vulnerable people died early, the number of deaths due to other causes like heart attacks, cancer, old age, diabetes etc. would be lower now than if covid never had happened.

I mostly look at the total deaths as a benchmark. The way they counted covid deaths changed and had new financial incentives which impacts numbers. Also, I would personally question the early accuracy of false/positive covid testing.

The numbers you suggest gets complicated by the fact that many people delayed care due to fear of leaving their houses, much less going to a covid-infested hospital.

How often do they update their baseline?

Their website has their charts and methodology pointing out the good and bad:

https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm...