A street battle favors the side with more reserves and the defender, that is the Union (all other times the Confederates were defending)
Why would the fall of one of the greatest fortresses in North America and the cutting in two of the CSA not effect European opinion
Why would great Britain want to recognize the CSA, they are importing corn from the Union and their trade with the Union is worth far more than with the CSA
Philadelphia is 100 miles from Gettysburg, even Harrisburg is 40, given Lee's stressed logistic situation I don't think he can advance that far and still have ammo to fight with after fighting a major battle