Can i ask a sythe adm or mod to print his infos? I think he probably used his email to register here. If that happened its a proof i guess since i will send the pm confirmations too. I didn't understand the second part of your reply. Could you explain better?
EDIT:
I think the fact that this skype (him) sent me the receipt (
http://prntscr.com/hrfhhn) proves that its hm, since he is the only one that has access to this, right?
Your not thinking about this right, imagine your paypal, you have no idea of who you are or who this guy is and need a way to determine that.
Step 1 is to establish that its him, whether through providing them with skype resolvers(if u can find a working one) or his IP or something for them to compare, u have to somehow prove that skype is attatched to the paypal account that's disputing.
Once u tied the two together then all the evidence u submit the paypal agent actually will know that the screenshots of him sending the receipt and talking to you are legitmate evidence, if u cant PROVE the skype and paypal are linked - any evidence u submit from the skype will be ignored/tossed out.
You need to in every form try to prove he's guility, u can audit his ip on Sythe and show them that hes banned and then provide links to his ban reasons(search RAS archive), you need to give them reasonable doubt that he may be untruthful.
Once u establish reasonable doubt you need to try to prove that it was delievered- proof of delivery(I,e-trade screens of runescape) will often times do this but if u don't have any ur missing ur ace in the hole.
After u submit everything make sure u submit a story and u explain exactly what happended, who he is, etc and u provide proof of ur claims.
Paypal is similar to Sythe, they want everything to tie together with a nice bow on top.
After u do all the above, call in(I recommend avoiding lunch hours and ending hours so check what time PST it is when ur calling), I've found mid day they also are quite rushed and just want u off the phone.
The best time to call is around 1 hour before closing or 30 minutes after they open in personal experience.
goodluck!