To get anything like that out through the API it first needs to be a metric. There is no metric for this out of the box so you would need to create a calculated service metric like below where your base metric is Request count and your condition is the Response time is under 1000ms.
Once you have done that this new metric will be calculated for all of your services (you can filter this down to only certain services with additional conditions). As a metric it will be available through the metrics API.
Regarding DDUs, I think everything is public already, and has been communicated to clients...
Interesting, because there is not a single reference here in the Community yet, but has been available for some weeks now in the documentation: