So if Hedwig has no bosom, how did zie pass the physical exam in order to marry that guy? Did zie just pass hirself off as amazingly flat-chested? Also, why didn't zie have breasts anyway? Or did zie just stop taking hormones and has a chest with No Ontological Inertia?
In one of the songs, Hedwig sings about how her mother made her 'tits of clay'. And, it's not like they would be doing a full cavity search or anything... "Do you, Insert Name Here, look male? Do you, Insert Name Here, look female? Good, you can marry." Any number of real life transgender individuals are proof enough of that.
The thing is, if they weren't doing very nearly a full cavity search, there wouldn't have been any need of the surgery. It's surprisingly easy to hide a standard set of gentleman's vegetables, even to the point of looking convincingly female while naked from certain angles. In the stage version, it's a bit clearer that Luther tricked Hedwig into thinking that the surgery was necessary, even though it wasn't really.
On the subject of the sex change, why the Hell does dilation never come up? Seriously, from Hedwig's account it doesn't even sound like the sex change operation was actually botched, it just sounds like she forgot to dilate. No mention.
Why does Hedwig's tattoo merge into a different one right at the end?
A big part of Hedwig's reason for pursuing Tommy is that she believes that Tommy is her soulmate, someone or something that will make her feel whole. Hence, the tattoo is initially a half, representing her feelings of incompleteness. By the end, she learns to be complete by her/himself, and the tattoo becomes a whole to reflect this.