You can look at monkit metrics for some of metrics. You will not find most of what you are looking for (e.g., there’s no latency for first byte), but at least there are some insights.
For the number of concurrent connections, you’d first need to define exactly what you need (max over some period of time, average, maybe some other metric?).
First byte latency should be easy to add in code if you’re willing to patch up your binary. You will be breaking T&C though.