Thanks for reporting.
1) will be fixed. @rashi put this in priority pipeline.
2) @rashi add an option to discount tax like we did in shipping.
Krzysztof point number 2 is very country-specific actually. in many countries even after the discount tax should be charged on the actual price of the product. Anyway, we will give an option for that.
ETA if you are a premium customer: 4 Work Weeks
ETA for community members: 8 workweeks.
On sponsoring and paying for these fixes, dev and fix will be started today itself.