I have read that this poem is grounded in a plot that was exporting communism to the USA through Alaska; that Dan McGrew was a USA intelligence officer; that the people that shot him were communist agents and that the "lady that was known as Lou was really Lenin’s girlfriend. I woujld like verification of this supposition.

Nope. Lenin was exiled to Siberia when the poem was written. It was published in 1907 when Lenin got out.
Sorry.
I think this is a dreampt up theory, of course it has been a while since i read that poem. I guess google it
For another good read, find the Cremation of Sam McGee. Robert Service was an exceptional poet in his day, in that he made quite a bit of money from his poetry.
utter nonsense. Its a Canadian poem, by a Canadian poet, and has nothing to do with the US or its paranoia