If you wish to alter the behaviour of SQL Prompt where it does not suggest variables over large blocks of SQL or fails to provide help with large scripts, you can edit the RedGate_SQLPrompt_Engine_EngineOptions.xml file.
This file should be in the below location:
%USERPROFILE%\\AppData\\Local\\Red Gate\\SQL Prompt 6
The string in the file you need to edit is <ParserLookBackDistance>5000</ParserLookBackDistance><ParserLookAheadDistance>3000</ParserLookAheadDistance>
The figure detailed here is in bytes. You can increase the look back distance as much as you like. However please be aware that, depending on your hardware, there may be a considerable degradation in the performance of the tool.
Please let me know if that helps.