For the first issue I'd ask you open a Support case as this is likely a bug in dashboard. I'm seeing the same behavior.
For number 2. The data is logged for 365 days. In the custom time range selector you can go back 365 days. But, you can only a view a max of 30 days at a time. So, for example you can view May 1, 2021 to May 30, 2021. Showing more than 30 days in the dashboard will require a feature enhancement.
For number 3 have you explored the MT API? You could potentially create scheduled calls to grab the sensor data and drop it to an external spot.
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