The guidance gives a range of solutions to common everyday situations, your situation does not fall into this category. So it is necessary to consider why the rule about the direction of opening was made - the potential hazards that are well understood and how those hazards can be controlled in this particular case.
The UK guidance is much less prescriptive than the EU Directive, the 50 /60 person guidance for inward opening doors is a UK thing, the directive states that all exits shall open in the direction of escape.
The hazard of an inward opening door is magnified in an assembly building. Could these hazards be realised in this particular case? Apply the guidance and turn the doors or reduce the numbers is the simple answer. However if you cannot change the doors or the numbers of persons then you need to evaluate the hazard and risk.
Are there other factors that could eliminate or mitigate the risk of persons being trapped behind the closed doors? Is there a good distance between the final exits, are they well separated, how will the flow of people down the staircase be controlled, where are the pinch points, what is the width of the staircase, how much space is there between the base of the staircase and the doors, how is the evacuation managed and controlled, how soon after the raising of the alarm will people arrive at the exits and at what rate will they arrive?
It may be possible to construct an argument for retaining the status quo taking the above points into consideration. But I would go for turning the doors if you can. That way you have an answer that will always work.
