787 conversions are on hold at the moment due to the engine problems. They are examining the possibility of re-starting in April/May but that is only the latest best guess. I think the previous plan was to have got rid of passenger 767s in 2020 but that will now be later (2021?) The freighters will remain for some time after that but I haven't seen a date for them disappearing and it may well depend on whether ANA get the 787 freighter or switch to the 777 freighter. Long and short of it; assume you're going to fly the 767 for quite some time yet.
Your other questions have been answered many times before, so have a good read of the thread because it's all there and you would need to miss more than one post to have your questions unanswered.