He is very suspicious. Besides he didn't want "big money" back, he made all this show first which looks very strange. If we'll look at the transaction he provided for proof of the payment it is a payment from an exchange account (what is clear from the screens as well), so we can't trace his own address. If we'll look at the chat correspondence we can see that he asked to refund his money not giving an address — to where did he want to get a refund? To an exchange address? Looks like a staging. And when he finally gave his address here for a refund we see that it is a totally new address not to be traced.

I don't know about LDL, but what I see doesn't look like proofs to be sure in any guilt on him. Specific style of writing of 2 is natural for Bengali and some other languages in Indian region so it is hardly an evidence of anything.

The entire situation is very strange.