We know there are some bugs with saving and we are fixing some of them in every update, that's why game is still is Pre-Alpha. Sorry for your lost save data :/
1) Yes, for sure we will add some new furnitures in the future.
2) We know that setting up lessons it quite tedious and we are thinking how to improve that. Maybe we will add copy/paste.
3) We have plans to add some new UI elements (also clock) in the 0.5.1 Update.
4) Currently no plans for that.
5) Speed time option will be available only in the build mode (as it is now). We want to add pause in the future updates.
6) You can schedule "free period" be not assigning any lesson. Then studens will go the the rest rooms, use vending machines etc.
Have a great day!