Exhaust NUTS off

[1999 Drifter]

Finally got the exhaust nuts of by using 8 sided thing that looks like a allen key, 
forgot the name 3/8 sae fits on socket wrench.
The reason the nuts were on so tight is the shop or someone did not use exhaust gaskets but figured if thet screwed them tight enough who ever bought the bike wouldn't find out till it was to late
So now it's putting back together time but first some questions

is re-jetting the carb the same as adjusting the air/fuel mixture screw?

does the outside temp effect the setting of air/ fuel mixture?  i.e warmer climate leaner mixture

I tried the air / fuel mixture at 2 turns out and she'd stall after 30 seconds(with exhaust leak), 3 1/2 turns out (with exhaust leak)seems to run fine but just wondering if it is to rich once the new exhaust gaskets are installed
are you confused yet
Thanks
1999 drifter 800