i agree that the borate should be beneficial as it adds buffering capacity. Seachem actually adds it to the salt intentionally - i dont think they would be doing that if they weren't convinced that it would have a positive effect.
you dont NEED to use the seachem alk kit with the salt, but it helps in that you can test how much of your alk is carbonate and how much is borate.
OK ,I just spoke to one of the salemans from seachem
How much salt do we need ,(amount of buckets .or bags?)
Reason is ,we can get free shipping if we buy over $3500 in salt ,,but that alot of salt