To clarify; when you had cross-save enabled, was your PSN account the active save? It sounds like you were using your PSN data to play on Steam, via cross-save. If that is correct; then by deactivating cross-save, you have removed the ability to access those characters anywhere but on a PlayStation console. Cross-save does not transfer data between accounts, it simply allows you to access the data from the active account, while playing on linked platforms.
As you have already deactivated cross-save, you will indeed have to wait 90 days before any of the involved platform accounts can be used in cross-save again. If the characters you were playing were in fact PSN based, then you will need to re-link that account, and retain access to that account for as long as you want to use that data. Otherwise, you would need to start fresh on your desired platform.
You can read more about how cross-save works, and the restrictions in its use, in the article below:
https://help.bungie.net/hc/en-us/articles/360049498031-Destiny-2-Cross-Save-Guide
Is it at all possible for my playstation data to be migrated/copied to my steam so it will have my playstation character data and the playstation data can be wiped? Way too much time to restart and it would be silly to give him my account and then tell him he can't touch Destiny 2, have to make an alt account to play that.