He agreed to ship 2-day - which, in itself, is pretty far from right - then later decided he wanted more money for a different shipping method. Although he states that the buyer agreed to his ex post facto stipulation, I'll remain skeptical until he posts screenshots to corroborate that claim. Thus far, he hasn't presented anything that would even suggest the buyer agreed to send more money.
That's more or less what this seems to hinge upon. IF the buyer agreed to the amended deal, then suddenly, inexplicably dropped all contact,
after having directly expressed no issues with the situation, then the seller looks to be in much stronger position. Given how little sense it would make for the buyer to agree to send more money, then silently pull a disappearing act, I'm operating under the assumption that there must be more communications that we're not being shown. I do have to say that the seller's choice to grossly misrepresent the weather doesn't paint a very flattering picture of his intentions.
However, we only have Evan's word on all of this
I think he's made it pretty clear that he has no intentions of issuing a refund. He's even gone as far as [falsely]
referring to the $445 payment as a "partial" payment, stating:
Apparently, he's the type of person who feels that the entire payment should be forfeit, if his belated demands aren't met.

At the time the money was sent - as per their initial agreement - it was payment in full. Even if Sloan's wildly unlikely portrayal of events ends up being completely true, he's still not justified in keeping more than a
reasonable housing/feeding fee - which I think would only be applicable if it can be shown that the buyer agreed to the amendment before ceasing communications. If the buyer didn't agree to it, that's the point at which he should have been due a full refund.