Elemental Nova LB is obviously Foes Elemental Nova build… If you read the thread I think he (and others) answer most of your questions… he doesnt have a build guide step by step levelling but you can get the idea what is better.
For the LICH… I dont think that there is an updated 7.10 build that matches your DoT Poison requirements… but the build guide has old Acolyte builds that might help you understand how to build it.
I agree 100% 
For the rest of your questions I am sure someone will give you a decent answer. Lots will have an “it depends” type response but I am sure someone will help. I am not great with the exact mechanics of the game… Just enough to be dangerous and have @Llama8 correct me each time…