+6 would be more reasonable, though still pretty beefy. Again assuming a 16 in the relevant score, at fifth level you're looking at +15 without even trying. Skill focus, synergy, and one of those +2, +2 feats, and you're up to +22--that seems a little bit high to me.

Most of these abilities seem too powerful. Take Second-Story man, for instance. For a three-level dip, you get a hefty bonus to a good number of stats, a thirty foot climb speed, a +8 bonus to all climb checks, and you still have a decent sneak attack. All of this by level 5. That's better than most prestige classes. (Look at Thief-acrobat, for instance.) Strength to those three skills doesn't make a lot of sense to me and I can't see it being a huge draw.

Or Streetfighter. Weapon Finesse for free, full sneak attack progression, adding dex to damage (double dex during sneak attacks), and the hamstring ability. Couple this with Daring Outlaw and three levels of Swashbuckler, and you are getting Dex, Strength, and Intelligence to damage (and my swashbucklers usually have all three of these in the positives), full sneak attack, and your enemies have become basically immobile.

Pickpocket isn't so bad--Charisma to Hide/Move Silently isn't overpowering, and Cutpurse isn't going to break the game too bad. The skill modifier is a bit much, though.