Why is my manager stalling me to decrease to part time? Since I asked 2 months ago he is saying he has to see how the budget looks in order to accommodate a part timer. Since I’ve asked, 2 nurses are leaving for other jobs. We currently have a PT

You answered your own question. People are leaving and he cannot fill the positions fast enough. You should have an employee hand book (Paper or online). There should be section regarding status change (FT, PT, PRN) and time limits to be able to change status. If you are within the guidelines, it's time for crucial conversation with your manager.

My thought is was always better to keep a staff member and grant request even if the request was inside the timeframe.

Do you work in a union hospital? If so contact your representative to help you. If not you should talk to your manager again and stress the importance and your need for part time work. Sometimes part timers will need to have 2 spots filled to make up the one full time position lost. It can actually be more expensive for the unit to accommodate unless part timers receive less benefits under part time work. I would say your manager should think twice as two persons already left, more may follow if they can get what they want else where. Just keep asking your manager and say a part time position is now open so there is no need to see how your request needs to be accommodated, it's already there and open.