To cut the story short he was persuading me to send the BTC first before he make payment which I refuse, he even told me to send half of the BTC which he will make full payment after I confirm payment i send the remaining BTC I also refuse,
this could have been your ever worst mistake should in case you give in by sending first.
Note__ scammers can go extra mile even by sending you money first in order to achieve what they need.
That is their new strategy used in scamming people nowadays, some will send you huge amount of voucher just to convinced you because i have also witness such, they first take the risk to send you little to get the big catch but lucky enough, this time the scammer fall a victim.
I have one question am I a scammer too or did I do wrong by not sending him his Etherume back because after this incident my conscience has been beating me.
stay safe.
Remember you asked him before the whole transaction begins the is he ready to risk it and he replied yes, he dug the pit for you but ended up falling into it, you're free mate, enjoy your 300 Ethereum because you are not a scammer but a candidate of favour.