Is there a virtual CURSOR controls for ST3?
No, you need to tap in the text field to position the cursor. But this is on my todo list.
In the meantime you could use a 3rd party keyboard like SwiftKey or Flesky. I think that should work, but I did not try it myself.
Actually, there is a builtin cursor function in the Apple keyboard since iOS12 which I wasn't aware of:
Long press space bar and then you can slide your finger around to move the cursor on the screen.