How many campden tablets for home brewed cider Homebrewing

I've brewed 10 ciders so far. These are 5 gallon batches and I've always crushed 5 campden tablets and added to the fermenter all at once after fermentation is complete. I let that sit for a week or so and then I keg the cider.
The last few ciders have had a strong sulphur smell.

I recently read a recipe in BYO magazine on hopped ciders. I followed the recipe there and it talks about only adding a single tablet per day until the free sulphites are 0.5-0.8 ppm molecular SO2. The article says this is to protect against spoilage. It references an online calculator at http://ift.tt/2xEuO32 I've tried using this calculator after using a PH paper (very inaccurate). The calculator always says 0.25 tablets. I've tried setting the values in the calculator to all kinds of numbers but it always says 0.25 tablets, so obviously I don't trust it.

1. If I'm kegging and putting this into a refrigerator, do I even need campden tablets?
2. If I do want to achieve 0.5-0.8 ppm, can anyone suggest a way to calculate how many tablets to use or should I just use 5 over 5 days?

Submitted October 14, 2017 at 05:00AM by albertgrimley http://ift.tt/2xEJ4J2 Homebrewing