So question 1, do I believe The Son of man has already came with clouds of heaven... yes I do. And, Jesus told the high priest that HE, HIMSELF would Christ coming in the clouds.
Mat 26:63 But Jesus held his peace. And the high priest answered and said unto him, I adjure thee by the living God, that thou tell us whether thou be the Christ, the Son of God.
Mat 26:64 Jesus saith unto him, Thou hast said: nevertheless I say unto you, Hereafter shall ye see the Son of man sitting on the right hand of power, and coming in the clouds of heaven.
How can i not believe that it's already happened when the bible says it has?
I disagree with your conclusion, and here is a part of the reason why:
I do not believe Jesus is here saying "
you, the high priest
[singular], will see [...etc...]".
The wording (which I've enlarged in your quote) actually shows as the following:
--
"THOU/YOU [SINGULAR] hast/have said" (THIS IS speaking of what
the guy [singular] just said); THEN
--[Jesus continues] "nevertheless I say unto
YOU [PLURAL], Hereafter [/from now]
YOU [PLURAL] shall see the
Son of man [1] sitting on the right hand of power, and [2] coming in the clouds of heaven." [<--that second one, I believe, often refers to "judgment"]
So, a few things to note about this passage:
--the distinct SINGULAR, and then PLURAL "you"... [think: the "proleptic 'you'"]
--ALL "
Son of man cometh/coming/shall come/etc" (see in your quote ^ above) passages refer to His Second Coming
to the earth (to judge and to reign)
--the two aspects "1 & 2"
do follow on from His first century Cross, but when viewing the other passages informing us of the details regarding the "chronology," we can see that this takes place over a vast amount of time (rather than
merely the events surrounding 70ad). Again, keeping the "proleptic 'you'" and "PLURAL 'you'" (2 of the 3x in this verse) in mind.
Presently, He is in heaven (1), then the other aspect (2) will occur... and this is what
Acts 3:21 is saying, "whom indeed it behooves heaven to receive
until the time
s of restoration
of all things of which God spoke by the mouth of His holy prophets
from the age." [all of the (remaining) OT prophecies... which are not,
as of yet, fully fulfilled, but WILL BE!]