None of it sounds suspicious on the face of it. The reason why each auction was lost for exactly 50 cents is almost certainly the fact that that is the "bid increment"--the minimum increment by which ebay will bump up the bidding--and so that is not suspicious at all. (The winning bidder's maximum bid was probably higher than yours by more than 50 cents.) The second chance offer may well have been based on precisely your losing maximum, which obviously happens to be synonymous with your max snipe amount, but anyway it is, naturally, visible to the seller. The one thing to be wary of, I would think, is to be sure it is not a scam second chance offer--check to see it is in your ebay mailbox. See other thread on this too.
The other bidders may have been using AS, or they may have been sniping manually. (Or did they place their bids before you and this is a case of ebay proxy bidding?)
Basically, I suspect you probably just need to get familiar with bid increments in the proxy bidding system of ebay. This is explained at the ebay help page, and you can dp a search for numerous clarifications on this board as well. If I've misunderstood your problem, sorry.