Firstly, I would like to highlight the point "Possibly a real scammer", he ain't a scammer, why? because i worked for him and still. Never faced any scam issues with him nor any delay in payment. Ofcourse its suspicious for asking 50% payment, that's general case beside taking it specifically for him.
Secondly, I have looked into your gamemode; do you really expect to get paid "50% (60€)" for that? I don't think that's even 25% worth the amount and you shouldn't be arguing over that because its noticeable.
I don't know if you know this but personally i would like to advice "Learn to respect, if you wanna be respected". By saying that i don't mean i am best scripter or better than you or lower than you. Infact noone is perfect developer, the more you learn the less it is; because the development filed is so diverse. Also now i would like to talk beside the scripter point of view, yea i know its suspicious to work for someone without knowing if he is legit or nope, but you could use a small amount of downpayment as startup not 50% upfront.
I hope you take my advice for your next work and deal, Good Luck