He will have to prove his establishment, he’s been here since before 2015, I am correct?,
Does he is member of any church? Does he is active in his community?, Does he have friends at work? Did he take any English course?
A lot of members applied by themselves for H&C but you need proof of your argument, and with proof I mean with a lot of documents which explain his story and if his story is verifiable or believable. He can also try with a lawyer or immigration consultant.
More experienced members in this forum can guide him of what support documents he needs.
All the best