Stale gas and rust juice inside exhaust??

[240sBoMex]

My car will be out in a couple of days after about 2 months of storage and its got half a tank of gas in there just as old. I was wondering will that gas gonna be bad for the engine with 120Km (plan on fuel filter replacing soon)?
I'm worried because I read sumthing about engine fogging, not sure what that is..
And, also from recently starting the car up, there's some nasty juice that looks like rust thats been spouting out of my muffler and making little orange puddles. I got crushed bent piping w/ N1 muffler but could it be that my pipings rusting inside??

Thx for reading,