Hi Franciele,
There is no limit to the number of rules. I am guessing that it is the number of promoted columns. For best performance, you'll want to use two techniques:
1) use calculated values to reduce overhead - you can do this by putting each text control in a section (within the cell) and then copy the section and paste it right next to the original text field and right click the text field in the newly pasted section and make it a calculated value. Then you'll add hide-show rules on these sections based on whether the current row is the actively editing row. You'll need to add a button to select the row for editing and that sets the active row to the current row's ID (you can use count(preceding-sibling::my:row)+1 for that. This will dramatically reduce the performance overhead.
2) use paging to limit the vertical display to 100 rows or so. paging is easy to add. just add the following XTP and go through the instructions.
Let me know if you need help.
Good luck!
Patrick Halstead
Project Manager at Qdabra