From your info, the pool will report correctly what the real hash rate is.
If the miner is constantly reporting higher, then there's something wrong with it's reporting.

Only other thing I can think of is it's sending hashes somewhere else that makes up the difference.

Well you can only buy hashpower to run solo of course.

I'd highly suggest you stay right away from MRR - had a few complaints to me about sending hash rate from MRR.
Alas in all cases it's either been a problem at their end, or miners connecting directly to the pool with banned firmware.
The complaints flared up when MRR wouldn't reimburse them for hashes not sent to the pool,
which, to be blunt, is a scam.
Cost for hash rate there was ridiculously high,
and since the number of hashes you get determines the chances of you getting a block,
overpaying for hash rate is simply reducing your chances of getting a block.

The issues with FuckHash are a long history of scamming and lying about the rewards for miners.
While I certainly don't like them, and certainly would not trust them for spending a lot on a large amount of hash rate,
alas they are the most reliable for buying hash rate at the moment.

The race is on to find the BTC before the Halving!!!!!