I'm sure it is stressful- the whole process and wanting to do things exactly according to the regiment. I'm afraid I don't have enough knowledge to know how much the 'success' rate depends on following the guide exactly. Some people have succeeded I believe just with the SN alone, although I understand following the guide seems best.
So, was the 12.30 your second dose? Again- please bear in mind I'm not massively knowledgeable but I believe there are 48 hour regiments but also ones that are shorter- similar to the process they do in assisted suicide clinics. Which one are you going with?
I hope there will be more knowledgeable people on soon to better help answer the question. I'm sorry you have all this anxiety.