What I would do in this situation is take off the back, disconnect the battery and see if it boots up, If that doesn't work then I would take out the memory and replace it with known working memory and see if it works. I have seen this previously and sometimes the Ram just needs to be reseated or replaced in most cases. If it turns on but still doesn't display. Connect it to the external monitor or tv. If it displays with no issues then your screen is bad. If it doesn't display then you possibly could have a board issue.

From the sounds of it you may need to just replace the screen and that should fix the problem.

Generally speaking yes the battery should be at 100% capacity (You will need to let it charge once you get it installed) but its is good to note that it may not display under your battery health. Being that its an 11 Pro you will get a notification that says not original battery but that doesn't stop it from performing as it should. Hope this helps

Unfortunately, there has been no ways that I have found to bypass the bitlocker key. In instances like this I would recommend replacing the harddrive. Since bitlocker is protecting the data that I on the drive. Side note: I would also recommend checking for the bitlocker key which would be in the Microsoft account associated with the laptop. The one you use to log in with.

To help the it not being aesthetically pleasing, I would get a sticker cover to go over it. This will cover the touch pad but would keep its functionality. Being that its a school computer I would see if they school IT Department would allow it or see if they can replace it for you.