In Act III scene 6 of Macbeth, what is Lennox saying in this speech and what does he actually mean?

Well done for spotting the gap between appearance and
reality in this speech, and the sarcasm of Lennox as he comments upon recent occurrences
in the kingdom of Scotland! As Lennox is seen talking to a Lord, he discusses his
suspicions of what has happened and the true nature of events. However, although he
reports the known facts, if we look carefully and what he says and how he says it, we
can see that he is being incredibly ironic, and he does not actually mean what he says
at all. Note his comment on Macbeth and his actions in killing Duncan's two
henchmen:

So
that, I say,

He has borne all things well, and I do
think,

that, had he Duncan's sons under his
key

(As, and't please Heaven, he shall not), they should
find

What 'twere to kill a father; so should
Fleance.

Clearly, Lennox does
not believe Macbeth has done "all things well," as he believes that if Macbeth had
access to Duncan's sons and to Fleance that they would soon meet the fate of others that
Macbeth has had close contact with. Throughout this entire speech, Lennox is discussing
his suspcions of Macbeth, ironically underlining the difference between Macbeth's
actions and his real motives.