I'm actually fine with the pacing as is. It makes for a more satisfying dramatic payoff of the story when the Big Reveal finally happens.
It would have been standard fare to have Jimmy be a badarse gangster from the first week, and they certainly alluded to that with the hijacking scene. But since it took 6 or 7 episodes to really build him up, when he finally started walking the walk I think it has been much more rewarding. And, frankly, much more plausible. I think it shows confidence in the material that the people telling the stories are willing to spend a bit of time with them before rushing them into something. (altho they have done that with one story line, and that irks me....)
One thing this series does that I don't think any mob/gangster story has done since The Godfather is make genuinely sympathetic characters out of villains. Shoot, they even managed to make Al Capone a sympathetic figure two episodes ago. Alphonse freakin' Capone. I don't think Scorsese has ever really managed to do it, and what I saw of The Sopranos didn't do it either. But it's a real trick to take murders and turn them into people the audience truly empathizes with and hopes for their success. When Al finally ascends to the top of the Chicago heap, I think I might almost cheer.
I like the character of the man in the mask - Richard Harrow. (not too subtle, that naming convention) He's possibly the most interesting character they've shown so far, and he has only had like five minutes of screen time. He and Chalky would make a fun pair.
And regarding Jimmy's girlfriend/fiancee/baby mama..... my wife nailed it right on the head when she guessed four or five episodes ago where that particular storyline was headed. Well done to Mrs Tif.