Can I apply for a visitor's visa to see a friend or will I be impacted
by his pending application?
Everyone in theory is approved or denied on their own merits. Even if a person is affected by a related persons crime, in your case chances of an adverse effect are remote considering you’re the one who reported the crime.
My friend sent an invitation letter for he and I. Should I have her
just send letter for me?
That of course would be preferable. Extricating yourself from an association with such a blatant law breaker would be viewed positively by all parties including UK immigration.
Will he be subject to a 10 year ban? Will the Home Office follow up on
He will if it’s investigated and conclusive evidence is established. Under the current immigration climate, that is very likely.Tolerance for illegal immigration is at perhaps an all time low.
1.2 RFL5.2 How long are applicants automatically refused for?
10 years if they practised deception (which includes using false
documentation) in support of a previous visa application.
None of my business, however why do you tolerate this and continue to associate with such a person? Perhaps your residence in Canada is tied to him? For your own sake consult an immigration & criminal attorney in Canada. I don’t know about Canadian law however sometimes knowing about a crime and not reporting it is in itself a crime and your residence in Canada could be in jeopardy.