I say tear it all down and put it all back together again twice...
after your finished that read your manual 3 times......then you can run it as much as you want and break whatever you want and you'll already know how to fix it
sorry just had to do that.....
on a serious side the shift point depends on how it is set... and the engine tuning.......if your running too rich it won't shift into 2nd
as far as the engine stalling when you hit full brake...I would suggest you go back to factory needle settings then set your idle stop screw according to the instructions...then tune your HSN after your happy with that you can tune the LSN....I use the pinch test on all my Nitros for the low speed.....
always do a few high speed passes after every adjustment to clear it out.....
and remember the temps are used to get you into the ballpark....
I run 3 Nitros and I've never put a temp gun to any of them..I use the sound of the exhaust,,,,the smoke trail and performance to tune them....
my 2.5 Tmaxx has at least 5 gallons on and it still runs fine....getting a little low on compression now but it still runs...
have fun
RCcanuck