Maybe I'm way off here, but Rumple always knew who he was, right? In one episode last season when he was in jail, Regina asked Gold, who he was, and he said Rumplestilsken, so if he crossed the town line what would he forget? He didn't have an alternate life like everyone else (except Jefferson and Regina).
The PTB have said that Rumple was only aware of his 'true' identity from the Pilot on (after he heard Emma say her name in Granny's), but there IS on-screen evidence suggesting that he may or may not have known who he was from the moment the curse deposited everyone in Storybrooke.
Regarding what he would lose were he to cross the town line, everything that Rumple has done has been geared towards getting to our world, waiting for his Dark Curse to be broken, and then setting out to find Bae.
Unfortunately, as Belle said in last night's episode, the 'wrinkle' of the 'secondary curse' created when Rumple brought magic to Storybrooke now means that if Rumple were to cross the town line to go and try to find Bae, he wouldn't remember him even if he did manage to find him.