I'm no expert, but I do have a degree in forensic science, so am in a better position to give an opinion than most on those wounds. In that opinion, they are complete BS.
The laceration isn't consistent with a slashing wound. It looks like something that has been done in a slow motion with a rough edge. There's obviously no stitches, nor has there been any. I'd also imagine that given the force required by a heavy blade to cut through clothing, would have caused some kind of trauma to his collar bone which would then be exhibiting some signs of injury ie bruising. I'll take a pot shot at this one and say I've seen very similar injuries to that caused by seatbelts after car accidents. He's from a car forum isn't he?
The alleged bullet wound is probably less convincing. People seem to greatly underestimate the internal injuries that the force and energy of a bullet can cause to the tissue, organs and bones surrounding the actual path of a bullet through a person. I'm also not a doctor, but I've never known of a case of an abdominal gunshot wound that hasn't required surgery to extensively explore the abdominal cavity for injuries other than the primary visible wounds. Essentially you wouldn't have two perfect little blood spots on your dressing depicting an entry/exit wound. More likely you'll have a fairly large surgical scar.
In fairness, we don't have all the info and I'm only judging from some degree level knowledge applied to one photograph, so could be entirely wrong in my evaluation. Really though, not much about the story seems to make sense. Strikes me as a guy who has faked the whole thing in a huge act of trollage.