Daily deltas with 1-day offset


I send data from my heat cost allocators to InfluxDB.

What I want to achieve is to display the consumtpion for every day as a bar in a bar chart in Grafana.

The data, however, comes in in an unsual way:
Instead of showing the live heat comsumption, these devices basically calculate a new total value every day at midnight, and then send this total value (along with live temperature updates, but these are irrelevant here) all day long until around midnight, where the day’s consumption is then added to the total again, and so forth…

I am facing three problems here:

1.) I have minutely data for every day, but for the total values, this is the same value all day long as described above. I am just interested in a single data point from the day, since they are all the same anyway. How can I accomplish this with Influx SQL?
For example, how can I pick a single data point that is closest to 1PM?

2.) With the resulting time series data of daily measurements, how can i calculate the daily consumptions (delta) from the total consumption?

3.) The daily deltas I would get then would still have the wrong date, since the total value “measured” from that day reflects yesterdays total. How could i realize a -1 day offset?