Repertoire Expansion #2: Meeting 1.e4 e5

Foreword: for what it's worth, my ICU rating is 1507, and I have no idea how that translates to a FIDE or any other rating! I'm useful, but have plenty of room to improve, and now that my studies are out of the way I plan on becoming more serious about my over-the-board chess. As such, I'm looking to expand my repertoire over the summer, and on the white side I'm looking for a better understanding of the classical open game. Specifically, I am considering the following:

• The Spanish/Ruy Lopez
• The Italian/Giuoco Piano
• The Scotch Gambit

On the Spanish Game...

This is almost stupidly popular at a high level, and has reams of theory behind it, but surely it also provides white with the most winning chances. I do have some idea of how to play Lopez positions, having briefly studied some lines perhaps a year or two ago, but I'm sure I could play the opening for years without ever really attaining a complete grasp of its intricacies and nuances. I will admit, of the three this is perhaps the one I am least drawn to in what I would call a romantic manner—my heart longs for wild King's Gambit positions—but chess isn't all heart. In fact, one might rightly point out that it's a far more logical game!
Questions:

• Just how challenging is the depth of theory in these lines?
• Would studying the Spanish teach me any more than studying the Italian Game, or does the attraction here lie primarily with the given winning chances?

On the Italian Game...

A conundrum, this. A timeless classical opening, rife with attacking possibilities from the Fried Liver to the Max Lange, yet one against which black can apparently equalise with relative ease. Of course, black's ability to equalise in certain lines is no reason to poo-poo the entire opening; there is much chess to be played once the middle game is reached, and much, I am sure, to learn from this grand old opening. To me, it seems to strike a middle ground between the other two openings I'm considering here; it's not quite as theoretical as the Ruy Lopez, but it may also be a little more solid than giving up a pawn in the opening.

Questions:

• Just how much theory does one need to know to play 3.Bc4 well?
• How reliable are the more aggressive lines that follow? I'm sure I'll learn a lot either way, but how often does the Giuoco Piano live up to its name?

On the Scotch Gambit...

Well I did mention the King's Gambit earlier; you should hardly be surprised at my willing to give up a pawn for a bit of fun. A clubmate of mine once recommended that I look at the Max Lange Attack, and I have to admit that it does seem very me... of course it can be gotten at via the Giuoco Piano, but the Scotch Gambit may be a more fun way by which to do so, and in and of itself this gambit line should offer plenty of attacking chances, and plenty of opportunities to enhance my understanding of the open game, albeit that it may teach me more in an attacking sense, whereas the Italian Game may further my education in a more rounded way.

Questions:

• Is this opening all about the attack, and will I risk ignoring positional development if I choose it over the Spanish or Italian games?
• From a practical sense, how do club players between 1500 and 1800 tend to fare with/against an opening of this nature? I suspect white players do fairly well up to a point, though I'm not entirely sure I should let that influence my decision, seeing as the primary goal here is to enhance my chess understanding.