Ex parte - means when the judge decides something without one or more of the parties being present. So the judge reviews the case and checks it meets the normal rules of the family court and the second one - directions is about the judge proposes the terms of the divorce settlement I think (been a long time since my divorce!)
The affadavit bit is a sworn statement. So I suppose its a judge deciding on the evidence what course is to be taken without either party being present. Obviously never heard of the plain english campaign.
I think (a) is deemed service ( judge deems the respondent has been served and you can apply for decree nisi) and (b) is substituted service (judge directs what you still have to do to ensure service, which will be different to the usual postal or personal service).