IDK maybe their hits inject glycotoxin into their victim (if said victim is a creature). I think adding a venom sac would mess up cross-breeding compatibility.
This isn't possible with genetics alone, but everything else should be. It would be interesting to see a breed where the males and females have different lifespans.
As for the .atts, when I did them manually I just opened each sprite image in paint, then used the .att files as coordinates to map the connection points. It's slow and tedious and not really recommended when better methods exist, but there's no maths required.