Have you checked out FmSearchResults from seedcode?
Not sure if it handles specifically what you're looking for or not. But it's powerful and I've used it as a substitute to quickfind before.
I have created somehting like this and it highlights the text as you are typing it and then once you hit return, it narrows down the list to the text entered. Caveat: it can be very slow on some computers...
To acheive this, you have a calc field that stores all the fields you wish to search, a global field that allows you to enter the text, the conditional highlight applied to text witin all the fields on the layout and it looks like you have already done this, the only real major difference is that there is a script trigger on the global field that commits after every keystroke (and I think there is a refresh screen) and then returns the cursor to where the user was typing, that way it works just the same way as your example, except that the matching text is highlighted before the "search" itself goes ahead. This could be useful???
Just like your example, once you hit tab or return (you need to capture these keystrokes in the script triggered when entering text into the field) then the "find" is performed.
I like the idea of the seedcode example, as it also illustrates the number of matches and it's darn quick! What I would be concerned about with searching across multiple tables like this is the security restrictions and revelvance to where you are. Perhaps a combination of my suggestion with the advanced features of the seedcode example might be a good solution!