Hi. Let me guess in there.
1- I guess when you export to excel it shows the format of the measure without caring about the visualization format. You can have measures with X decimals configured and change that for a certain visual. Excel files may be able to handle format while csv are only text plain values. Check your measures data type format. Make them fixed decimal and pick the number of decimals. I think that should solve the export.
2 and 3 this is a new feature that might be preview yet. You can submit the issue in here to help Power Bi team to solve it: https://community.powerbi.com/t5/Issues/idb-p/Issues
I hope that helps,
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Happy to help!