Rumpelstiltskin claims he needed the dark curse to find his son. However, there was probably an easier way he could have traveled to the real world, as we've seen with various other characters. In "The Return", the blue fairy tells Rumpel that she used up the last magic bean. However, he finds more in "The Crocodile". Though Hook gets away with them, Rumpel could have fought harder, being the dark one and all. It would have been much easier than casting the dark curse. If Snow White was able to send Emma to the real world through a magic wardrobe, Rumpel should have been powerful enough to do the same. Then he could have found his son 21 years earlier (after he escaped from Neverland) and continue to raise him as a teenager. He also never considered going to Neverland to save his son. He definitely knew Bae was there because he knew he was still alive over a century later. The sourcerer's apprentice was able to send himself and other characters to the real world. However, it makes sense that the apprentice has this power that Rumpel doesn't have. Though the apprentice was clearly opposed to helping Rumpel due to their history together, Rumpel could have manipulated the apprentice into sending him to the real world. My explanation for all of this is that Rumpel wanted to find Bae, but was not willing to give up magic to do so. The dark curse was the only way he could come to the real world and still have magic. This shows that Rumpel never chooses his son over magic, at least not until season 3.
Deals Rumpelstiltskin made where his objectives were unclear:
In "That Still Small Voice" it is unclear what Rumpelstiltskin wanted to do with the puppets. He still has them with him in Storybrooke. Since they are technically not dead, it is possible that Geppeto will reconnect with his parents in the future.
In "The Price of Golf", he wants Cinderella's firstborn child. However, he obviously knows that the curse is coming and she won't give birth to her baby on time. Did he make this deal just so Emma would owe him a favor? If so, what favor was he planning on getting? He wasn't planning on having Emma come with him to find his son until "In the Name of the Brother". This is implied when he has no problem with Emma dying in "Queen of Hearts" and is about to go by himslef to find Bae in "The Outsider". Maybe Rumpel made the deal to have leverage on Emma or Ashley for a future favor that was not thought of at the time.