Heya!
Are you sure that these are facing the wrong direction? eg do you have any reference?
I would assume that it is correct so pilots know where they are when they turn off the runway? Or do all of those signs say something runway releated?
Please don't mix A300 with A310 topics..
The cabin wouldn't depressurise in that case, at least not rapidly, but when the start rotary is on start a/b the bleed air will be used for the start of the engines.
All of the times I have seen it on the forum here, it is due to the name not entered correctly. Tell him to double check that he entered the "Simbrief Alias" in the field on the EFB