I have been growing chillies for 4+ decades, you will find most of the superhots will be a little less reliable for germination than the average say cayenne, this is normal.
To get 6 from the 7 sown is not bad, in truth you will probably only need 1 plant unless you have asbestos lined you know what
You have paid well over the top truth be told, typically I pay around £2.50-£3 for 10 seeds for the superhots.
Hope they are productive and you enjoy the munching of them.