You could have got a BTS for a little more!
A big trans pan is usless just takes more time to heat then cool the fluid. Big waste of $$.
Tunes will not help trans temps!..have you checked the trans fluid flow? Your sig shows a 6.0 cooler so your temps should not be that high unless your pulling and its 100* plus!
If they instaled a HD TQ did they mod the pump properly?