Try this: create milestones after each of these tasks and put deadlines on the milestones, then link tasks to them as appropriate.

If you have any constraints set as the result of entering start dates or end dates, remove them. You should have only As Late As Possible constraints.

Then flip the project to being planned from a Start Date and I think you will have your dates.

BE SURE to save copies of your file along the way, in case I don't know what I am talking about. and I might not; I don't think I have ever needed to do what you need to do.