When is it okay to cancel a sale?

[jhs5120]

After all this talk regarding cancelling transactions, screwing seller/buyers and people reneging; I wanted to share a current situation I'm in:

I had a large group of sets for sale at $2,400 obo. In the listing I charged $100 shipping, but asked for pick-up, because I was unsure about the logistics involved in shipping such a heavy (over 120 pounds) group of items. The sets are probably worth $1,800-2,000 if you price them out individually.

I have been in communications with a man (buyer A) who offered $1,700 off ebay for the group. I accepted, but he stopped emailing me. During his messaging hiatus, another bidder (Buyer B) bought the lot for the full asking price! The bidder who won the lot was a 0 feedback bidder who created his account two days before buying my lot. He lives in NY (I live in NJ) and paid immediately.

First red flag: Paypal held the funds for two days while they were trying to verify the source of the payment to ensure it was legitimate. PayPal never provided further details, but the eventually verified it and passed it along.

Second red flag: I don't like dealing with new bidders, especially new bidders who buy an expensive item without caring for the price paid. I recently was scammed buy a zero feedback bidder who charged back his credit card 8 months after the transaction was complete. PayPal ruled against me.

Third red flag: Even though he paid the $100 shipping, I emailed him requesting to meet somewhere in North Jersey (half way) to drop off the items. I offered him his $100 shipping refunded and another 1975 Topps set (about $250 value) on top of the sets he just purchased. He declined saying he was bed ridden. Normally, a person would jump on the offer. It's very possible he's telling the truth, but it sounds a lot like "my dad is very sick and I'm selling his cards" type thing.

Forth red flag: I then reply, "I'm sorry to hear you're not well, I would be happy to hand deliver the cards. It would be much easier (and cheaper) than shipping out 5 boxes." He never replied.

Now, somewhere in between the third red flag and forth red flag "Buyer A" emails me asking if the sets are still available. I inform him of the situation and let him know that I do not feel comfortable shipping 5 or so boxes to this 0 feedback buyer. After an email conversation with "Buyer A" I decided to message "Buyer B" telling him that I must insist on pick-up/hand delivery or I would need to cancel the transaction. He has yet to reply (it's been 5 days).

My question: Is this a situation where it's kosher to cancel a sale? "Buyer B" has a legal right to these cards, but I am honestly not comfortable dealing with him. Something about splitting two grand worth of sets into 4 or 5 boxes and mailing them to a zero feedback bidder doesn't sit well with me. Especially one who has been acting a little bit off since the transaction first took place. I'm obviously not worried about the money; "Buyer B" already paid $2,500 and "Buyer A" is offering $1,700, but I'd gladly pay $800 for a little piece of mind.

I know many members here argue against reneging no matter what, but I'm genuinely curious what people here think. Also, if I do continue with the "Buyer B" transaction, is there a way to ensure he doesn't screw me down the road? i.e. returns my sets and swap out the valuable ones with bricks.