Late to the party....comparing the 2 videos, 5k launch (in slow mo) is crushing the tire and making it unload the chassis, where as your 3500 launch is not. Have you tried meeting in the middle on the launch RPM (4250)....maybe 4250-4500 would still give you a decent light, and possibly not kill the tire?
Are you on radials? I know others have said it, but more tire pressure may help....even if you can put it into a controlled spin (not ideal, but may work).
Sorry, I'm not too much help on the setup since I'm a foot-braker and my Caltracs are setup for that...and I leave at about 2500.
